U.S. patent application number 15/733208 was filed with the patent office on 2020-11-26 for adhesive articles including a cushion layer and a continuous shell layer.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Ross E. Behling, Zhong Chen, Chaodi Li, Jingjing Ma, Eric D. Shockey, Peter M. Simone, Sharon Wang, David J. Yarusso.
Application Number | 20200369926 15/733208 |
Document ID | / |
Family ID | 1000005075202 |
Filed Date | 2020-11-26 |
View All Diagrams
United States Patent
Application |
20200369926 |
Kind Code |
A1 |
Yarusso; David J. ; et
al. |
November 26, 2020 |
ADHESIVE ARTICLES INCLUDING A CUSHION LAYER AND A CONTINUOUS SHELL
LAYER
Abstract
An adhesive article including: a flexible backing; a first
cushion layer permanently bonded to a first surface of the flexible
backing, wherein the first cushion layer: has an average thickness
of at least 10 micrometers; and includes an acrylate
pressure-sensitive adhesive having a Fox Tg of up to -30.degree.
C., wherein the acrylate pressure-sensitive adhesive includes a
(meth)acrylate copolymer; and a first continuous shell layer
adjacent the first cushion layer, wherein: the first continuous
shell layer has an average thickness of up to 25 micrometers; the
ratio of the first cushion layer average thickness to the first
shell layer average thickness is at least 2:1; the first continuous
shell layer includes an adhesive having a Fox Tg of -20.degree. C.
to +50.degree. C.; and the first continuous shell layer adhesive
includes a copolymer having a weight average molecular weight of at
least 100,000 Daltons.
Inventors: |
Yarusso; David J.;
(Shoreview, MN) ; Behling; Ross E.; (Woodbury,
MN) ; Simone; Peter M.; (Woodbury, MN) ; Li;
Chaodi; (Woodbury, MN) ; Chen; Zhong;
(Woodbury, MN) ; Wang; Sharon; (St. Paul, MN)
; Ma; Jingjing; (Cottage Grove, MN) ; Shockey;
Eric D.; (Stillwater, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000005075202 |
Appl. No.: |
15/733208 |
Filed: |
December 14, 2018 |
PCT Filed: |
December 14, 2018 |
PCT NO: |
PCT/IB2018/060125 |
371 Date: |
June 10, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62608673 |
Dec 21, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 428/2848 20150115;
Y10T 428/2891 20150115; C09J 2301/302 20200801; C09J 133/08
20130101; C09J 7/385 20180101; C09J 2301/208 20200801; C09J 2433/00
20130101; Y10T 428/28 20150115 |
International
Class: |
C09J 7/38 20060101
C09J007/38; C09J 133/08 20060101 C09J133/08 |
Claims
1. An adhesive article comprising: a flexible backing; a first
cushion layer permanently bonded to a first surface of the flexible
backing, wherein the first cushion layer: has an average thickness
of at least 10 micrometers; and comprises an acrylate
pressure-sensitive adhesive having a Fox Tg of up to -30.degree.
C., wherein the acrylate pressure-sensitive adhesive comprises a
(meth)acrylate copolymer comprising: a) one or more (meth)acrylate
monomeric units of Formula (I) in an amount of at least 60 wt-%,
based on a total weight of monomeric units in the (meth)acrylate
copolymer: ##STR00009## wherein: R.sub.1 is hydrogen or a methyl
group; and R.sub.2 is an alkyl, heteroalkyl, aryl, aralkyl, or
alkaryl group with the proviso that the first monomeric unit of
Formula (I) with R.sub.2 having at least 8 carbon atoms is present
in an amount of at least 20 wt-%, based on a total weight of
monomeric units in the (meth)acrylate copolymer; and b) one or more
polar monomeric units in an amount of up to 7 wt-%, based on a
total weight of monomeric units in the (meth)acrylate copolymer;
wherein the sum of all monomeric units of the first cushion layer
(meth)acrylate copolymer equals 100% by weight; and a first
continuous shell layer adjacent the first cushion layer, wherein:
the first continuous shell layer has an average thickness of up to
25 micrometers; the ratio of the first cushion layer average
thickness to the first shell layer average thickness is at least
2:1; the first continuous shell layer comprises an adhesive having
a Fox Tg of -20.degree. C. to +50.degree. C.; and the first
continuous shell layer adhesive comprises a copolymer having a
weight average molecular weight of at least 100,000 Daltons,
wherein the copolymer comprises: a) one or more low Tg
(meth)acrylate monomeric units of Formula (II) in an amount of at
least 25 wt-%, based on a total weight of monomeric units in the
copolymer: ##STR00010## wherein: R.sub.1 is hydrogen or a methyl
group; and R.sub.3 is an alkyl, heteroalkyl, aryl, aralkyl, or
alkaryl group having 2 to 24 carbon atoms; b) one or more polar
monomeric units in an amount of up to 5 wt-%, based on a total
weight of monomeric units in the copolymer; and c) one or more high
Tg nonpolar monomeric units in an amount of at least 35 wt-%, based
on a total weight of monomeric units in the copolymer; wherein the
sum of all monomeric units of the first shell layer copolymer
equals 100% by weight.
2. The adhesive article of claim 1 wherein the acrylate
pressure-sensitive adhesive of the first cushion layer has a Fox Tg
of at least -85.degree. C.
3. The adhesive article of claim 1 wherein the ratio of the first
cushion layer average thickness to the first shell layer average
thickness is at least 3:1 and up to 300:1.
4. The adhesive article of claim 1 wherein the first cushion layer
(meth)acrylate copolymer comprises one or more (meth)acrylate
monomeric units of Formula (I) wherein R.sub.2 is an alkyl group
having 1 to 24 carbon atoms.
5. The adhesive article of claim 4 wherein the first cushion layer
(meth)acrylate copolymer comprises one or more (meth)acrylate
monomeric units of Formula (I) derived from monomers selected from
the group of 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate,
ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl
(meth)acrylate, cyclohexyl (meth)acrylate, hexyl (meth)acrylate,
2-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl
(meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate,
isostearyl (meth)acrylate, behenyl (meth)acrylate, 2-methylbutyl
(meth)acrylate, and combinations thereof.
6. The adhesive article of claim 1 wherein the first cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units derived from monomers selected from the group of
(meth)acrylic acid, (meth)acrylamide, alkyl-substituted
(meth)acrylamides, and combinations thereof.
7. The adhesive article of claim 1 wherein the first shell layer
copolymer comprises one or more polar monomeric units in an amount
of at least 0.5 wt-%, based on a total weight of monomeric units in
the copolymer.
8. The adhesive article of claim 1 wherein the first shell layer
copolymer comprises one or more low Tg (meth)acrylate monomeric
units of Formula (II) wherein R.sub.3 is an alkyl group having 2 to
24 carbon atoms.
9. The adhesive article of claim 8 wherein the first shell layer
copolymer comprises one or more low Tg (meth)acrylate monomeric
units of Formula (II) derived from monomers selected from the group
of 2-ethylhexyl (meth)acrylate, ethyl acrylate, n-butyl acrylate,
isobutyl acrylate, hexyl (meth)acrylate, 2-octyl acrylate, isooctyl
acrylate, isononyl acrylate, isostearyl acrylate, 2-methylbutyl
acrylate, and combinations thereof.
10. The adhesive article of claim 1 wherein the first shell layer
copolymer comprises one or more polar monomeric units derived from
monomers selected from the group of (meth)acrylic acid,
(meth)acrylamide, alkyl-substituted (meth)acrylamides, and
combinations thereof.
11. The adhesive article of claim 1 wherein the first shell layer
copolymer comprises one or more high Tg nonpolar monomeric units
derived from monomers selected from the group of styrene,
substituted styrene, isobornyl (meth)acrylate, methyl
(meth)acrylate, tert-butyl (meth)acrylate, iso-butyl methacrylate,
cyclohexyl (meth)acrylate, norbornyl (meth)acrylate, and
combinations thereof.
12. The adhesive article of claim 1 wherein the first cushion layer
(meth)acrylate copolymer further comprises vinyl acetate monomeric
units in an amount of up to 7 wt-%, based on the total weight of
monomeric units in the copolymer.
13. The adhesive article of claim 1 wherein the first shell layer
copolymer further comprises vinyl acetate monomeric units in an
amount of up to 7 wt-%, based on the total weight of monomeric
units in the copolymer.
14. The adhesive article of claim 1 wherein the first cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units having an acid group and the first shell layer copolymer
comprises one or more polar monomeric units having a basic
group.
15. The adhesive article of claim 1 wherein the first cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units having a basic group and the first shell layer copolymer
comprises one or more polar monomeric units having an acidic
group.
16. The adhesive article of claim 1 wherein the first cushion layer
(meth)acrylate copolymer has a weight average molecular weight of
at least 100,000 Daltons and up to 2,000,000 Daltons.
17. The adhesive article of claim 1 which demonstrates an increase
in 1800 angle peel adhesion strength at a peel rate of 0.2 in/min
(0.08 mm/sec) from stainless steel at room temperature compared to
an adhesive article having the same flexible backing and first
cushion layer but without the first shell layer.
18. The adhesive article of claim 17 which demonstrates at least an
increase in 1800 angle peel adhesion strength at a peel rate of 0.2
in/min (0.08 mm/sec) from stainless steel or polypropylene at a
temperature of up to 65.degree. C. compared to an adhesive article
having the same flexible backing and first cushion layer but
without the first shell layer.
19. The adhesive article of claim 17 which demonstrates an average
rolling ball stopping distance according to a Rolling Ball Tack
Test of at least 200 mm.
20. The adhesive article of claim 1 further comprising: a second
cushion layer permanently bonded to a second surface of the
flexible backing, wherein the second cushion: has an average
thickness of at least 10 micrometers; and comprises an acrylate
pressure-sensitive adhesive having a Fox Tg of up to -30.degree.
C., wherein the acrylate pressure-sensitive adhesive comprises a
(meth)acrylate copolymer comprising: a) one or more (meth)acrylate
monomeric units of Formula (I) in an amount of at least 60 wt-%,
based on a total weight of monomeric units in the (meth)acrylate
copolymer: ##STR00011## wherein: R.sub.1 is hydrogen or a methyl
group; and R.sub.2 is an alkyl, heteroalkyl, aryl, aralkyl, or
alkaryl group with the proviso that the second monomeric unit of
Formula (I) with R.sub.2 having at least 8 carbon atoms is present
in an amount of at least 20 wt-%, based on a total weight of
monomeric units in the (meth)acrylate copolymer; and b) one or more
polar monomeric units in an amount of up to 7 wt-%, based on a
total weight of monomeric units in the (meth)acrylate copolymer;
wherein the sum of all monomeric units of the second cushion layer
(meth)acrylate copolymer equals 100% by weight; and a second
continuous shell layer adjacent the second cushion layer, wherein:
the second continuous shell layer has an average thickness of up to
25 micrometers; the ratio of the second cushion layer average
thickness to the second shell layer average thickness is at least
2:1; the second continuous shell layer comprises an adhesive having
a Fox Tg of -20.degree. C. to +50.degree. C.; and the second
continuous shell layer adhesive comprises a copolymer having a
weight average molecular weight of at least 100,000 Daltons,
wherein the copolymer comprises: a) one or more low Tg
(meth)acrylate monomeric units of Formula (II) in an amount of at
least 25 wt-%, based on a total weight of monomeric units in the
copolymer: ##STR00012## wherein: R.sub.1 is hydrogen or a methyl
group; and R.sub.3 is an alkyl, heteroalkyl, aryl, aralkyl, or
alkaryl group; b) one or more polar monomeric units in an amount of
up to 5 wt-%, based on a total weight of monomeric units in the
copolymer; and c) one or more high Tg nonpolar monomeric units in
an amount of at least 35 wt-%, based on a total weight of monomeric
units in the copolymer; wherein the sum of all monomeric units of
the second shell layer copolymer equals 100% by weight.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/608,673, filed Dec. 21, 2017, the
disclosure of which is incorporated by reference herein in its
entirety.
BACKGROUND
[0002] Pressure sensitive adhesives are well known and used in many
industrial applications. It is also known that optimization of such
adhesives for a given application requires a balance of properties
that are often in opposition to one another. The properties
typically desired are peel adhesion strength (at a variety of
speeds and temperatures), tack or rapid bonding with minimal
pressure, and shear resistance or ability to hold loads for
extended time. For example, one often sees that increases in shear
resistance are accompanied by reductions in tack and/or peel
adhesion strength. Adhesives designed for good tack and peel at
room temperature and moderate peel speeds may have poor peel
adhesion strength at low peel rates and/or high temperature.
Improving the high temperature and/or low speed peel adhesion
strength, however, often results in low tack.
[0003] The need for a better combination of adhesion performance at
room temperature and at high temperature along with better
performance on low energy surfaces is common in many applications
(e.g., in the automotive and electronics bonding areas) under ever
more demanding requirements, particularly where high temperature
lifting resistance and relatively low tack are desirable
properties. Thus, there continues to be a need for new adhesive
articles.
SUMMARY
[0004] Provided herein are adhesive articles that include a cushion
layer and a continuous shell layer. Such two-layer adhesives can
provide a unique balance of properties and design control for
different applications.
[0005] More specifically, provided herein is an adhesive article
including: a flexible backing; a first cushion layer permanently
bonded to a first surface of the flexible backing, wherein the
first cushion layer: has an average thickness of at least 10
micrometers; and includes an acrylate pressure-sensitive adhesive
having a Fox Tg (glass transition temperature) of up to -30.degree.
C., wherein the acrylate pressure-sensitive adhesive includes a
(meth)acrylate copolymer; and a first continuous shell layer
adjacent the first cushion layer, wherein: the first continuous
shell layer has an average thickness of up to 25 micrometers; the
ratio of the first cushion layer average thickness to the first
shell layer average thickness is at least 2:1; the first continuous
shell layer includes an adhesive having a Fox Tg of -20.degree. C.
to +50.degree. C.; and the first continuous shell layer adhesive
includes a copolymer having a weight average molecular weight of at
least 100,000 Daltons.
[0006] The acrylate pressure-sensitive adhesive of the first
cushion layer includes a (meth)acrylate copolymer including:
[0007] a) one or more (meth)acrylate monomeric units of Formula (I)
in an amount of at least 60 percent by weight (wt-%), based on a
total weight of monomeric units in the (meth)acrylate
copolymer:
##STR00001## [0008] wherein: [0009] R.sub.1 is hydrogen or a methyl
group; and [0010] R.sub.2 is an alkyl, heteroalkyl, aryl, aralkyl,
or alkaryl group; with the proviso that the first monomeric unit of
Formula (I) with R.sub.2 having at least 8 carbon atoms is present
in an amount of at least 20 wt-%, based on a total weight of
monomeric units in the (meth)acrylate copolymer; and
[0011] b) one or more polar monomeric units in an amount of up to 7
wt-%, based on a total weight of monomeric units in the
(meth)acrylate copolymer;
[0012] wherein the sum of all monomeric units (i.e., monomeric
units (a) and (b) plus any optional monomeric units) of the first
cushion layer (meth)acrylate copolymer equals 100% by weight.
[0013] The first continuous shell layer adhesive (which may be a
pressure-sensitive adhesive) includes a copolymer having a weight
average molecular weight of at least 100,000 Daltons, wherein the
copolymer includes:
[0014] a) one or more low Tg (meth)acrylate monomeric units of
Formula (II) in an amount of at least 25 wt-%, based on a total
weight of monomeric units in the copolymer:
##STR00002## [0015] wherein: [0016] R.sub.1 is hydrogen or a methyl
group; and [0017] R.sub.3 is an alkyl, heteroalkyl, aryl, aralkyl,
or alkaryl group;
[0018] b) one or more polar monomeric units in an amount of up to 5
wt-%, based on a total weight of monomeric units in the copolymer;
and
[0019] c) one or more high Tg nonpolar monomeric units in an amount
of at least 35 wt-%, based on a total weight of monomeric units in
the copolymer;
[0020] wherein the sum of all monomeric units (i.e., monomeric
units (a), (b), and (c) plus any optional monomeric units) of the
first shell layer copolymer equals 100% by weight.
[0021] As used herein, the term "(meth)acrylate" refers to a
methacrylate and an acrylate.
[0022] As used herein, the term "(meth)acrylamide" refers to a
methacrylamide and an acrylamide.
[0023] As used herein, the term "adjacent" can be used to refer to
two materials, typically in the form of layers, that are in direct
contact or that are separated by one or more other materials, such
as a flexible backing layer and an adhesive layer with a chemical
primer layer there between. Often, adjacent materials are in direct
contact (e.g., an adhesive layer directly disposed on a flexible
backing layer).
[0024] As used herein, an asterisk (*) shows the location of
attachment of the monomeric unit to another group or monomeric
unit.
[0025] According to the Pressure-Sensitive Tape Council,
pressure-sensitive adhesives (PSAs) are defined to possess the
following properties: (1) aggressive and permanent tack, (2)
adherence with no more than finger pressure, (3) sufficient ability
to hold onto an adherend, and (4) sufficient cohesive strength to
be removed cleanly from the adherend. Materials that have been
found to function well as PSAs include polymers designed and
formulated to exhibit the requisite viscoelastic properties
resulting in a desired balance of tack, peel adhesion, and shear
holding power. PSAs are characterized by being normally tacky at
room temperature (e.g., 20.degree. C.). Materials that are merely
sticky or adhere to a surface do not constitute a PSA; the term PSA
encompasses materials with additional viscoelastic properties.
[0026] This criterion defines a pressure sensitive adhesive as an
adhesive having a 1 second creep compliance of greater than
1.times.10.sup.-6 cm.sup.2/dyne as described in Handbook of
Pressure Sensitive Adhesive Technology, Donatas Satas (Ed.),
2.sup.nd Edition, p. 172, Van Nostrand Reinhold, New York, N.Y.,
1989. Alternatively, since modulus is, to a first approximation,
the inverse of creep compliance, pressure sensitive adhesives may
be defined as adhesives having a Young's modulus of less than
1.times.10.sup.6 dynes/cm.sup.2.
[0027] Glass Transition Temperature (Tg) values may also be
calculated using the Fox equation. The calculation is based on the
weighted average of the individual homopolymer glass transition
values. For a copolymer prepared from n different monomers, the
inverse of the Tg of the copolymer is equal to the summation of the
weight fraction of each component divided by the Tg of that
particular component (expressed in absolute temperature units, such
as Kelvin). That is, for a copolymer prepared from n components,
1/Tg of the copolymer is equal to (weight fraction of component
one/Tg of component one)+(weight fraction of component two/Tg of
component two)+(weight fraction of component 3+Tg of component 3)+
. . . +(weight fraction of component n/Tg of component n). Lists of
glass transition temperatures for homopolymers are available from
multiple monomer suppliers such as from BASF Corporation (Houston,
Tex., USA), Polyscience, Inc. (Warrington, Pa., USA), and Aldrich
(Saint Louis, Mo., USA) as well as in various publications such as,
for example, Mattioni et al., J. Chem. Inf Comput. Sci., 2002, 42,
232-240.
[0028] As used herein, "alkyl" refers to a monovalent group that is
a radical of an alkane and includes straight-chain, branched,
cyclic, and bicyclic alkyl groups, and combinations thereof. Unless
otherwise indicated, the alkyl groups typically contain from 1 to
24 carbon atoms. There can be at least 2, at least 3, or at least 4
carbon atoms and up to 24, up to 20, up to 18, up to 16, up to 12,
up to 10, up to 6, up to 4, or up to 3 carbon atoms. In some
embodiments, the alkyl groups contain 1 to 20 carbon atoms, 1 to 10
carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3
carbon atoms. In certain embodiments, the alkyl groups include 2 to
24 carbon atoms or 4 to 24 carbon atoms. Examples of "alkyl" groups
include, but are not limited to, methyl, ethyl, n-propyl, n-butyl,
n-pentyl, isobutyl, t-butyl, isopropyl, n-octyl, n-heptyl,
ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl,
norbornyl, and the like.
[0029] The term "aryl" refers to a monovalent group that is
aromatic and, optionally, carbocyclic. The aryl has at least one
aromatic ring. Any additional rings can be unsaturated, partially
saturated, saturated, or aromatic. Optionally, the aromatic ring
can have one or more additional carbocyclic rings that are fused to
the aromatic ring. Unless otherwise indicated, the aryl groups
typically contain from 6 to 30 carbon atoms. There can be at least
10, or at least 14 carbon atoms and up to 24, up to 20, up to 18,
up to 12, or up to 10 carbon atoms. In some embodiments, the aryl
groups contain 6 to 24, 6 to 20, 6 to 18, 6 to 16, 6 to 12, or 6 to
10 carbon atoms. Examples of an aryl group include phenyl,
naphthyl, biphenyl, phenanthryl, and anthracyl.
[0030] The term "aralkyl" refers to a monovalent group that is an
alkyl group substituted with an aryl group (e.g., as in a benzyl
group). The term "alkaryl" refers to a monovalent group that is an
aryl substituted with an alkyl group (e.g., as in a tolyl group).
Unless otherwise indicated, for both groups, the alkyl portion
often has 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4
carbon atoms, and an aryl portion often has 6 to 24 carbon atoms, 6
to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6
to 12 carbon atoms, or 6 to 10 carbon atoms.
[0031] The term "heteroalkyl" means an alkyl group having at least
one --CH.sub.2-- replaced with a heteroatom such as NR, O, or S,
wherein R is H or an alkyl group. There can be more than one
heteroatom such as 1 to 10, 1 to 6, 1 to 4, or 1 to 3 heteroatoms.
The number of carbons is the same as described for an alkyl group.
The heteroatom can replace any --CH.sub.2-- in the alkyl group but
two heteroatoms are separated by at least one --CH.sub.2--
group.
[0032] The phrase "permanently bonded" in the context of a bond
formed between an adhesive (particularly a pressure-sensitive
adhesive) and a flexible backing means the bond fails cohesively
before adhesive failure from the flexible backing is observed when
the adhesive is stressed by some means (most commonly a peel or
tensile mode).
[0033] The term "comprises" and variations thereof do not have a
limiting meaning where these terms appear in the description and
claims. Such terms will be understood to imply the inclusion of a
stated step or element or group of steps or elements but not the
exclusion of any other step or element or group of steps or
elements. By "consisting of" is meant including, and limited to,
whatever follows the phrase "consisting of." Thus, the phrase
"consisting of" indicates that the listed elements are required or
mandatory, and that no other elements may be present. By
"consisting essentially of" is meant including any elements listed
after the phrase and limited to other elements that do not
interfere with or contribute to the activity or action specified in
the disclosure for the listed elements. Thus, the phrase
"consisting essentially of" indicates that the listed elements are
required or mandatory, but that other elements are optional and may
or may not be present depending upon whether or not they materially
affect the activity or action of the listed elements. Any of the
elements or combinations of elements that are recited in this
specification in open-ended language (e.g., comprise and
derivatives thereof), are considered to additionally be recited in
closed-ended language (e.g., consist and derivatives thereof) and
in partially closed-ended language (e.g., consist essentially, and
derivatives thereof).
[0034] The words "preferred" and "preferably" refer to embodiments
of the disclosure that may afford certain benefits, under certain
circumstances. However, other claims may also be preferred, under
the same or other circumstances. Furthermore, the recitation of one
or more preferred claims does not imply that other claims are not
useful and is not intended to exclude other claims from the scope
of the disclosure.
[0035] In this application, terms such as "a," "an," and "the" are
not intended to refer to only a singular entity but include the
general class of which a specific example may be used for
illustration. The terms "a," "an," and "the" are used
interchangeably with the term "at least one." The phrases "at least
one of" and "comprises at least one of" followed by a list refers
to any one of the items in the list and any combination of two or
more items in the list.
[0036] As used herein, the term "or" is generally employed in its
usual sense including "and/or" unless the content clearly dictates
otherwise.
[0037] The term "and/or" means one or all of the listed elements or
a combination of any two or more of the listed elements.
[0038] Also, herein, all numbers are assumed to be modified by the
term "about" and in certain embodiments, preferably, by the term
"exactly." As used herein in connection with a measured quantity,
the term "about" refers to that variation in the measured quantity
as would be expected by the skilled artisan making the measurement
and exercising a level of care commensurate with the objective of
the measurement and the precision of the measuring equipment used.
Herein, "up to" a number (e.g., up to 50) includes the number
(e.g., 50).
[0039] Also, herein, the recitations of numerical ranges by
endpoints include all numbers subsumed within that range as well as
the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,
5, etc.).
[0040] As used herein, the term "room temperature" refers to a
temperature of 20.degree. C. to 25.degree. C. or 22.degree. C. to
25.degree. C.
[0041] The term "in the range" or "within a range" (and similar
statements) includes the endpoints of the stated range.
[0042] Groupings of alternative elements or embodiments disclosed
herein are not to be construed as limitations. Each group member
may be referred to and claimed individually or in any combination
with other members of the group or other elements found therein. It
is anticipated that one or more members of a group may be included
in, or deleted from, a group for reasons of convenience and/or
patentability.
[0043] When any such inclusion or deletion occurs, the
specification is herein deemed to contain the group as modified
thus fulfilling the written description of all Markush groups used
in the appended claims.
[0044] When a group is present more than once in a formula
described herein, each group is "independently" selected, whether
specifically stated or not. For example, when more than one R group
is present in a formula, each R group is independently
selected.
[0045] Reference throughout this specification to "one embodiment,"
"an embodiment," "certain embodiments," or "some embodiments,"
etc., means that a particular feature, configuration, composition,
or characteristic described in connection with the embodiment is
included in at least one embodiment of the invention. Thus, the
appearances of such phrases in various places throughout this
specification are not necessarily referring to the same embodiment
of the invention. Furthermore, the particular features,
configurations, compositions, or characteristics may be combined in
any suitable manner in one or more embodiments.
[0046] The above summary of the present disclosure is not intended
to describe each disclosed embodiment or every implementation of
the present invention. The description that follows more
particularly exemplifies illustrative embodiments. In several
places throughout the application, guidance is provided through
lists of examples, which examples may be used in various
combinations. In each instance, the recited list serves only as a
representative group and should not be interpreted as an exclusive
list. Any of the elements that are positively recited in this
specification as alternatives may be explicitly included in the
claims or excluded from the claims, in any combination as desired.
Although various theories and possible mechanisms may have been
discussed herein, in no event should such discussions serve to
limit the claimable subject matter.
BRIEF DESCRIPTION OF FIGURES
[0047] FIG. 1 is a cross-sectional representation of an embodiment
of an adhesive article of the present disclosure (not necessarily
to scale).
[0048] FIG. 2 is a cross-sectional representation of another
embodiment of an adhesive article of the present disclosure (not
necessarily to scale).
DETAILED DESCRIPTION
[0049] Provided herein are adhesive articles that include a cushion
layer and a continuous shell layer. The continuous shell layer is
the outer layer that comes in contact with the target substrate to
which the adhesive article is applied. It is thinner and includes
an adhesive having a higher glass transition temperature (Tg) than
that of the cushion layer.
[0050] Selection of the materials for the cushion layer and the
shell layer can provide a unique balance of properties for a
variety of applications. For example, the two-layer adhesives can
provide better combination of adhesion performance at room
temperature and at higher temperatures along with better
performance on low energy surfaces. Significantly, in certain
embodiments, adhesive articles of the present disclosure
demonstrate enhanced adhesion at low peel rates and/or high
temperatures while still retaining useful tack, compared to either
of the single adhesive layers used alone, which would be lacking in
one or both performance attributes. Furthermore, such advantages
can be achieved without the need to use a foam in the core or any
component of the adhesive article, which is desirable for
applications in which optical transparency, incompressibility, or
thinner overall constructions are desired. Neither the core nor
that shell is typically a foam.
[0051] The ability to modify the tack very precisely is a highly
desirable performance attribute of adhesives, particularly PSAs.
Furthermore, to do this with only a nominal impact on the total PSA
performance (e.g., shear and peel behavior) would be highly
desirable. In one example, the placement and positioning of large
graphic films with PSA attachments on a vehicle, such as used in
the commercial graphics business, can be quite challenging
requiring many different solutions. To aid placement while avoiding
immediate PSA adhesion, these solutions range from the application
of soap and water to the vehicle prior to adhesion, to more
complicated solutions requiring non-tacky ceramic posts to be
adhered to the surface of the PSA. Such posts effectively reduce
the peel performance of the PSA by reducing area of adhesion onto
the vehicle.
[0052] The adhesive articles of the present disclosure provide a
unique solution to overcome these challenges. The use of a higher
Tg adhesive in a shell layer on an underlying PSA not only allows
for positioning of the article, but also can enhance the final PSA
performance. This can be achieved, for example, by adjusting the
thickness of the higher Tg adhesive shell layer and thus changing
the tack (or rolling ball distance) of the article. Additionally,
increasing the Tg of the higher Tg continuous shell layer may also
decrease the tack (or inversely increase the rolling ball
distance).
[0053] As shown in FIG. 1, an adhesive article (e.g., tape) 10 of
the present disclosure includes a flexible backing 12 having a
first surface 14 and a second surface 16, a first cushion layer 20
permanently bonded to the first surface 14 of the flexible backing
12, and a first continuous shell layer 22 adjacent the first
cushion layer 20.
[0054] Herein, use of the term "first" does not necessarily require
that there has to be a second cushion layer and/or a second
continuous shell layer, although in certain embodiments, the
adhesive articles do include a second cushion layer and a second
continuous shell layer. Thus, as shown in FIG. 2, in certain
embodiments, an adhesive article 30 of the present disclosure
includes a flexible backing 32 having a first surface 34 and a
second surface 36, a first cushion layer 40 permanently bonded to
the first surface 34 of the flexible backing 32, a first continuous
shell layer 42 adjacent the first cushion layer 40, as well as a
second cushion layer 46 permanently bonded to the second surface 36
(i.e., second side) of the flexible backing 32, and a second
continuous shell layer 48 adjacent the second cushion layer 46.
[0055] The ability to tune the adhesive properties of the first
shell layer 42 independently of the second shell layer 48 may allow
for enhanced peel performance when bonding dissimilar substrates to
either surface of the adhesive article. For example, an adhesive
article of the present disclosure could include a relatively low Tg
first shell layer 42 to position adjacent a first substrate and a
relatively high Tg second shell layer 48 to position adjacent a
second substrate. The second substrate could be more easily
positioned and aligned relative to the first substrate prior to
creating a bond.
[0056] Herein, reference to a cushion layer includes reference to a
first and/or second cushion layer, and reference to a shell layer
includes reference to a first and/or second shell layer.
[0057] A cushion layer (first and/or second) has an average
thickness of at least 10 micrometers. In certain embodiments, a
cushion layer has an average thickness of at least 20 micrometers,
at least 30 micrometers, or at least 50 micrometers and up to 150
micrometers, up to 125 micrometers, up to 100 micrometers, up to 75
micrometers, or up to 50 micrometers.
[0058] A continuous shell layer has an average thickness of up to
25 micrometers. Above this thickness the continuous shell layer may
behave as a self-supporting film of the shell by itself and thus
negate the beneficial effects of the bilayer construction. In
certain embodiments, a continuous shell layer has an average
thickness of up to 20 micrometers, up to 12 micrometers, up to 10
micrometers, up to 8 micrometers, up to 6 micrometers, up to 4
micrometers, or up to 2 micrometers.
[0059] A ratio of the cushion layer average thickness to the shell
layer average thickness is at least 2:1. In certain embodiments,
the ratio of the cushion layer average thickness to the continuous
shell layer average thickness is at least 3:1, at least 4:1, at
least 5:1, at least 10:1, at least 20:1, at least 50:1, or at least
70:1. In certain embodiments, the ratio of the cushion layer
average thickness to the shell layer average thickness is up to
300:1, up to 200:1, up to 100:1, or up to 50:1.
[0060] The relatively thin shell layer that includes the higher Tg
adhesive provides an increase in the debonding force required to
separate the adhesive from a substrate, in comparison to the
debonding force of the lower Tg adhesive of the underlying cushion
layer alone. Additionally, the lower Tg adhesive of the cushion
layer provides the necessary conformability for good substrate
wetting and energy dissipation that would be lacking in the higher
Tg adhesive of the overlying shell layer alone. These composite
properties are what leads to the significant improvement in bond
performance (i.e., peel force/resistance) observed for the adhesive
articles of the present disclosure.
[0061] In certain embodiments, an adhesive article of the present
disclosure demonstrates an increase (in certain embodiments, at
least a two-fold increase, or at least a three-fold increase) in
180.degree. angle peel adhesion strength at a peel rate of 0.2
inch/minute (0.08 millimeter/second) from stainless steel at room
temperature compared to an adhesive article having the same
flexible backing and first cushion layer but without the first
shell layer, if measured on the first side of the adhesive article
(or the second cushion layer but without the second shell layer, if
measured on the second side of the adhesive article).
[0062] Herein, "peel rate" refers to the rate of propagation of the
peel front relative to the substrate to which the adhesive is
applied. That is, the speed of pulling the tape relative to the
peel front rate depends on the peel angle. For example, when
peeling at an angle of 180 degrees, the peel front rate is one-half
the pulling speed.
[0063] In certain embodiments, an adhesive article of the present
disclosure demonstrates an increase (in certain embodiments, at
least a two-fold increase, or at least a three-fold increase) in
180.degree. angle peel adhesion strength at a peel rate of 0.2
inch/minute (0.08 millimeter/second) from stainless steel at a
temperature of up to 65.degree. C. compared to an adhesive article
having the same flexible backing and first cushion layer but
without the first shell layer, if measured on the first side of the
adhesive article (or the second cushion layer but without the
second shell layer, if measured on the second side of the adhesive
article).
[0064] In certain embodiments, an adhesive article of the present
disclosure demonstrates an increase (in certain embodiments, at
least a two-fold increase, or at least a three-fold increase) in
180.degree. angle peel adhesion strength at a peel rate of 0.2
inch/minute (0.08 millimeter/second) from polypropylene at a
temperature of 65.degree. C. compared to an adhesive article having
the same flexible backing and first cushion layer but without the
first shell layer, if measured on the first side of the adhesive
article (or the second cushion layer but without the second shell
layer, if measured on the second side of the adhesive article).
[0065] In certain embodiments, an adhesive article of the present
disclosure demonstrates an average rolling ball stopping distance
according to a Rolling Ball Tack Test (as described in Examples
Section) of at least 200 millimeters (mm), at least 300 mm, or at
least 400 mm.
Cushion Layer Acrylate Pressure-Sensitive Adhesive
[0066] A cushion layer (first and/or second) includes an acrylate
pressure-sensitive adhesive having a Fox Tg of up to -30.degree. C.
The Fox Tg can be, for example, up to -35.degree. C., up to
-40.degree. C., up to -45.degree. C., or up to -50.degree. C. In
certain embodiments, the acrylate pressure-sensitive adhesive of
the cushion layer has a Fox Tg of at least -85.degree. C., at least
-80.degree. C., at least -75.degree. C., at least -70.degree. C.,
at least -65.degree. C., or at least -60.degree. C.
[0067] In certain embodiments, a cushion layer (meth)acrylate
copolymer has a weight average molecular weight of at least 100,000
Daltons, at least 150,000 Daltons, at least 200,000 Daltons, at
least 300,000 Daltons, or at least 400,000 Daltons. In certain
embodiments, a cushion layer (meth)acrylate copolymer has a weight
average molecular weight of up to 2,000,000 Daltons, up to
1,500,000 Daltons, up to 1,000,000 Daltons, up to 700,000 Daltons,
or up to 500,000 Daltons.
[0068] The acrylate pressure-sensitive adhesive of the cushion
layers (first and/or second) includes a (meth)acrylate copolymer
that includes:
[0069] a) one or more (meth)acrylate monomeric units of Formula
(I):
##STR00003## [0070] wherein: [0071] R.sub.1 is hydrogen or a methyl
group; and [0072] R.sub.2 is an alkyl, heteroalkyl, aryl, aralkyl,
or alkaryl group; and
[0073] b) one or more polar monomeric units.
[0074] The one or more (meth)acrylate monomeric units (a) of
Formula (I) are present in a cushion layer (meth)acrylate copolymer
in an amount of at least 60 wt-%, at least 65 wt-%, at least 70
wt-%, at least 75 wt-%, or at least 80 wt-%, based on a total
weight of monomeric units in the (meth)acrylate copolymer. In
certain embodiments, a cushion layer (meth)acrylate copolymer
includes one or more (meth)acrylate monomeric units (a) of Formula
(I) in an amount of up to 99.5 wt-%, up to 95 wt-%, up to 90 wt-%,
or up to 85 wt-%, based on a total weight of monomeric units in the
(meth)acrylate copolymer.
[0075] The one or more polar monomeric units (b) are present (i.e.,
they are present in an amount of greater than 0 wt-%) in a cushion
layer (meth)acrylate copolymer in an amount of up to 7 wt-%, up to
6 wt-%, up to 5 wt-%, or up to 4 wt-%, based on a total weight of
monomeric units in the (meth)acrylate copolymer. In certain
embodiments, a cushion layer (meth)acrylate copolymer includes one
or more polar monomeric units (b) in an amount of at least 0.5
wt-%, at least 1 wt-%, at least 1.5 wt-%, at least 2 wt-%, at least
2.5 wt-%, or at least 3 wt-%, based on a total weight of monomeric
units in the (meth)acrylate copolymer.
[0076] Herein, the sum of all monomeric units (a) and (b) and any
optional monomeric units of the cushion layer (meth)acrylate
copolymer equals 100% by weight.
[0077] In Formula (I) of the monomeric units of the cushion layer
(meth)acrylate copolymer, R.sub.2 is an alkyl, heteroalkyl, aryl,
aralkyl, or alkaryl group. Alkyl groups often have 1 to 24 carbon
atoms, 4 to 24 carbon atoms, 4 to 20 carbon atoms, 2 to 20 carbon
atoms, 4 to 12 carbon atoms, 2 to 12 carbon atoms, or 2 to 10
carbon atoms. Heteroalkyl groups often have 2 to 24, 4 to 24 carbon
atoms, 4 to 20 carbon atoms, or 4 to 12 carbon atoms. Aryl groups
often have 6 to 24 carbon atoms, 6 to 20 carbon atoms, 6 to 12
carbon atoms, or 6 to 10 carbon atoms. Aralkyl and alkaryl groups
often have an aryl or arylene portion with 6 to 20 carbon atoms, 6
to 12 carbon atoms, or 6 to 10 carbon atoms and an alkyl or
alkylene portion with 1 to 10 carbon atoms, 1 to 6 carbon atoms, or
1 to 4 carbon atoms.
[0078] In certain embodiments of Formula (I) of the monomeric units
of the cushion layer (meth)acrylate copolymer, R.sub.2 is an alkyl
group having 1 to 24 carbon atoms. In certain embodiments of
Formula (I) of the monomeric units of the cushion layer
(meth)acrylate copolymer, R.sub.2 is an alkyl group having 4 to 24
carbon atoms.
[0079] In certain embodiments, the monomeric unit of Formula (I) of
the monomeric units of the cushion layer (meth)acrylate copolymer
includes R.sub.2 groups having at least 8 carbon atoms (e.g., alkyl
groups with at least 8 carbon atoms). In such embodiments, these
monomeric units are present in an amount of at least 20 wt-%, at
least 25 wt-%, at least 30 wt-%, at least 35 wt-%, at least 40 wt-%
or even higher, based on a total weight of monomeric units in the
(meth)acrylate copolymer. In some embodiments, all the monomeric
units (a) of Formula (I) have at least 8 carbon atoms. That is, the
amount of these monomer units can be in a range of 20 wt-% to 99.5
wt-% based on a total weight of monomeric units in the
(meth)acrylate copolymer. The amount is often up to 99 wt-%, up to
95 wt-%, up to 90 wt-%, up to 85 wt-%, up to 80 wt-%, up to 75
wt-%, up to 70 wt-%, up to 65 wt-%, or up to 60 wt-%.
[0080] In certain embodiments, a cushion layer (meth)acrylate
copolymer includes one or more (meth)acrylate monomeric units of
Formula (I) derived from monomers such as 2-ethylhexyl
(meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate,
n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl
(meth)acrylate, hexyl (meth)acrylate, 2-octyl (meth)acrylate,
isooctyl (meth)acrylate, isononyl (meth)acrylate, isobornyl
(meth)acrylate, norbornyl (meth)acrylate, isostearyl
(meth)acrylate, behenyl (meth)acrylate, 2-methylbutyl
(meth)acrylate, and combinations thereof. In certain embodiments, a
cushion layer (meth)acrylate copolymer includes one or more
(meth)acrylate monomeric units of Formula (I) derived from monomers
selected from the group of 2-ethylhexyl acrylate, n-butyl acrylate,
isooctyl acrylate, 2-octyl acrylate, and combinations thereof.
Various isomer mixtures of the alkyl (meth)acrylates can be used as
those described, for example, in PCT Patent Application Publication
WO 2012/088126 (Clapper et al.).
[0081] In certain embodiments, a cushion layer (meth)acrylate
copolymer includes one or more polar monomeric units that are
derived from polar monomers. As used herein, the term "polar
monomer" refers to a monomer having a single ethylenically
unsaturated group and a polar group selected from the group of a
hydroxyl group, an acidic group, a basic group (such as a primary
amido group, a secondary amido group, a tertiary amido group, or an
amino group). In contrast, herein "nonpolar monomer" does not
include such polar groups.
[0082] The polar group can be in the form of a salt. For example,
the acidic group can be in the form of an anion and can have a
cationic counter ion. In many embodiments, the cationic counter ion
is an alkaline metal ion (e.g., sodium, potassium, or lithium ion),
an alkaline earth ion (e.g., calcium, magnesium, or strontium ion),
an ammonium ion, or an ammonium ion substituted with one or more
alkyl or aryl groups. The various amido or amino groups can be in
the form of a cation and can have an anionic counter ion. In many
embodiments, the anionic counter ion is a halide, acetate, formate,
sulfate, phosphate, or the like.
[0083] Useful acid-functional monomers include acrylic acid,
methacrylic acid, itaconic acid, maleic acid, fumaric acid, and
combinations thereof. Anhydrides, such as maleic anhydride and
methacrylic acid anhydride can also be used. The anhydrides can be
ring opened to provide acid groups.
[0084] Useful hydroxyl-functional monomers typically have a
hydroxyl equivalent weight of less than 400. The hydroxyl
equivalent molecular weight is defined as the molecular weight of
the monomeric compound divided by the number of hydroxyl groups in
the monomeric compound. Useful monomers of this type include
2-hydroxyethyl acrylate and methacrylate, 3-hydroxypropyl acrylate
and methacrylate, 2-hydroxypropyl acrylate and methacrylate,
4-hydroxybutyl acrylate and methacrylate, 2-hydroxyethylacrylamide,
and 3-hydroxypropylacrylamide. Additionally, hydroxyl functional
monomers based on glycols derived from ethylenoxide or
propyleneoxide can also be used. Various combinations of such
monomers can be used, if desired.
[0085] Polar monomers may also include amido groups, such as
primary amido groups including (meth)acrylamide, and secondary
amido groups including N-alkyl (meth)acrylamides (e.g., N-methyl
(meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl
(meth)acrylamide, N-tert-octyl (meth)acrylamide, or N-octyl
(meth)acrylamide), and tertiary amido groups including N-vinyl
caprolactam, N-vinyl-2-pyrrolidone, (meth)acryloyl morpholine, and
N,N-dialkyl (meth)acrylamides (e.g., N,N-dimethyl (meth)acrylamide,
N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, and
N,N-dibutyl (meth)acrylamide).
[0086] Polar monomers may also include an amino group such as
various N,N-dialkylaminoalkyl (meth)acrylates and
N,N-dialkylaminoalkyl (meth)acrylamides. Examples include, but are
not limited to, N,N-dimethylaminoethyl (meth)acrylate,
N,N-dimethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl
(meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide,
N,N-diethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl
(meth)acrylamide, N,N-diethylaminopropyl (meth)acrylate, and
N,N-diethylaminopropyl (meth)acrylamide.
[0087] In certain embodiments, a cushion layer (meth)acrylate
copolymer comprises one or more polar monomeric units derived from
polar monomers selected from the group of (meth)acrylic acid,
(meth)acrylamide, alkyl-substituted (meth)acrylamides (e.g.,
N,N-dimethyl acrylamide), and combinations thereof.
[0088] One or more optional other monomeric units may be included
in a cushion layer (meth)acrylate copolymer of the present
disclosure.
[0089] In certain embodiments, a cushion layer (meth)acrylate
copolymer further includes vinyl acetate monomeric units.
Generally, vinyl acetate is used as a scavenger of residual
(meth)acrylate monomers as described in U.S. Pat. No. 8,263,718
(Ellis). Typically, such vinyl monomeric units are present in an
amount of up to 7 wt-%, based on the total weight of monomeric
units in the copolymer. For example, the amounts can be up to 5
wt-%, up to 3 wt-%, up to 2 wt-%, or up to 1 wt-%. The amount, if
present, is often at least 0.1 wt-%, at least 0.2 wt-%, at least
0.5 wt-%, or at least 1 wt-%, In addition to a (meth)acrylate
copolymer, in certain embodiments, a cushion layer acrylate
pressure-sensitive adhesive further includes one or more additives
selected from the group of colorants, fillers, flame retardants,
antioxidants, UV-stabilizers, viscosity modifiers, and combinations
thereof. For example, antioxidants and/or UV stabilizers such as
hydroquinone monomethyl ether (4-methoxyphenol, MeHQ), and that
available under the trade name IRGANOX 1010
(tetrakis(methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamnate))meth-
ane) from BASF Corp., can be mixed with the cushion layer
(meth)acrylate copolymer to increase its temperature stability. If
used, an antioxidant and/or stabilizer is typically used in the
range of 0.01 wt-% to 1.0 wt-%, based on the total weight of the
acrylate pressure-sensitive adhesive. For example, the amounts can
be at least 0.01 wt-%, 0.02 wt-%, at least 0.05 wt-%, at least 0.1
wt-%, or at least 0.2 wt-% and up to 1.0 wt-%, up to 0.8 wt-%, up
to 0.6 wt-%, or up to 0.5 wt-%.
[0090] In certain embodiments, a cushion layer acrylate
pressure-sensitive adhesive includes tackifiers and/or plasticizers
in a combined amount of no more than 20 wt-%. The amount can be up
to 18 wt-%, up to 16 wt-%, up to 15 wt-%, up to 12 wt-%, or up to
10 wt-%, The amount can be at least 0.1 wt-%, at least 0.2 wt-%, at
least 0.5 wt-%, at least 1 wt-%, at least 2 wt-%, or at least 5
wt-%, In certain embodiments, a cushion layer acrylate
pressure-sensitive adhesive includes substantially no tackifiers
and/or plasticizers. In this context, "substantially no" means less
than 1 wt-%, less than 0.5 wt-%, or less than 0.1 wt-%, based on
the total weight of the acrylate pressure-sensitive adhesive.
[0091] The copolymers and adhesives of the cushion layer may be
prepared by any conventional polymerization method (such as
solution polymerization or emulsion polymerization) including
thermal bulk polymerization under adiabatic conditions, as is
disclosed in U.S. Pat. No. 5,637,646 (Ellis) and U.S. Pat. No.
5,986,011 (Ellis et al.). Other methods of preparing (meth)acrylate
copolymers include the continuous free radical polymerization
methods described in U.S. Pat. No. 4,619,979 (Kotnour et al.) and
U.S. Pat. No. 4,843,134 (Kotnour et al.), the polymerization within
a polymeric package as described in U.S. Pat. No. 5,804,610 (Hamer
et al.), and the on-web polymerization process as described in U.S.
Pat. No. 4,181,752 (Martens et al.). Alternatively, the copolymers
and adhesives of the cushion layer may be prepared as exemplified
in the Examples Section.
Shell Layer Adhesive
[0092] A continuous shell layer (first and/or second) includes an
adhesive (in certain embodiments, a pressure-sensitive adhesive)
that has a Fox Tg of -20.degree. C. to +50.degree. C. In certain
embodiments, the adhesive of the continuous shell layer has a Fox
Tg of up to +40.degree. C., up to +30.degree. C., or up to
+20.degree. C. and at least -15.degree. C., at least -10.degree.
C., at least -5.degree. C., or at least 0.degree. C.
[0093] A continuous shell layer (first and/or second) includes a
copolymer having a weight average molecular weight of at least
100,000 Daltons. In certain embodiments, a shell layer copolymer
has a weight average molecular weight of at least 150,000 Daltons,
at least 200,000 Daltons, at least 250,000 Daltons, at least
300,000 Daltons, at least 350,000 Daltons, or at least 400,000
Daltons. In certain embodiments, a first shell layer copolymer has
a weight average molecular weight of up to 2,000,000 Daltons, up to
1,500,000 Daltons, up to 1,000,000 Daltons, up to 700,000 Daltons,
or up to 500,000 Daltons.
[0094] The continuous shell layer adhesive may be a
pressure-sensitive adhesive.
[0095] The continuous shell layer adhesive copolymer includes:
[0096] a) one or more low Tg (meth)acrylate monomeric units of
Formula (I) (which may be the same or different than that of the
cushion layer):
##STR00004## [0097] wherein: [0098] R.sub.1 is hydrogen or a methyl
group; and [0099] R.sub.3 is an alkyl, heteroalkyl, aryl, aralkyl,
or alkaryl group;
[0100] b) one or more polar monomeric units (which may be the same
or different than that of the cushion layer); and
[0101] c) one or more high Tg nonpolar monomeric units.
[0102] Herein, a low Tg monomeric unit is derived from a low Tg
monomer, wherein a homopolymer of such monomer has a Tg of no
greater than 0.degree. C., no greater than -10.degree. C., or no
greater than -20.degree. C.
[0103] Herein, a high Tg monomeric unit is derived from a high Tg
monomer, wherein a homopolymer of such monomer has a Tg of greater
than 0.degree. C., greater than 10.degree. C., greater than
20.degree. C., or greater than 40.degree. C.
[0104] The one or more low Tg (meth)acrylate monomeric units (a) of
Formula (II) are present in a shell layer copolymer in an amount of
at least 25 wt-%, at least 30 wt-%, at least 35 wt-%, or at least
40 wt-%, based on a total weight of monomeric units in the
copolymer. In certain embodiments, a shell layer copolymer includes
one or more low Tg (meth)acrylate monomeric units (a) of Formula
(I) in an amount of up to 64.5 wt-%, up to 60 wt-%, up to 55 wt-%,
or up to 50 wt-%, based on a total weight of monomeric units in the
copolymer.
[0105] The one or more polar monomeric units (b) are present (i.e.,
they are present in an amount of greater than 0 wt-%) in a shell
layer copolymer in an amount of up to 5 wt-%, up to 4.5 wt-%, up to
4 wt-%, or up to 3.5 wt-%, based on a total weight of monomeric
units in the copolymer. In certain embodiments, a shell layer
copolymer includes one or more polar monomeric units (b) in an
amount of at least 0.5 wt-%, at least 1 wt-%, at least 1.5 wt-%, or
at least 2 wt-%, based on a total weight of monomeric units in the
copolymer.
[0106] The one or more high Tg nonpolar monomeric units (c) are
present in a shell layer copolymer in an amount of at least 35
wt-%, at least 40 wt-%, at least 45 wt-%, or at least 50 wt-%,
based on a total weight of monomeric units in the copolymer. In
certain embodiments, a shell layer copolymer includes one or more
high Tg nonpolar monomeric units in an amount of up to 74.5 wt-%,
up to 70 wt-%, up to 65 wt-%, or up to 60 wt-%, based on a total
weight of monomeric units in the copolymer.
[0107] Herein, the sum of all monomeric units (a), (b), and (c) and
any optional monomeric units of the shell layer copolymer equals
100% by weight.
[0108] In Formula (II) of the monomeric units of the shell layer
copolymer, R.sub.2 is an alkyl, heteroalkyl, aryl, aralkyl, or
alkaryl group. In certain embodiments of Formula (II) of the
monomeric units of the shell layer copolymer, R.sub.2 is an alkyl
group having 2 to 24 carbon atoms. In certain embodiments of
Formula (II), R.sub.3 is an alkyl group having 4 to 24 carbon
atoms, 4 to 20 carbon atoms, 2 to 20 carbon atoms, 4 to 12 carbon
atoms, 2 to 12 carbon atoms, or 2 to 10 carbon atoms. In other
embodiments, R.sub.3 is a heteroalkyl, aryl, aralkyl, or alkaryl
group. Heteroalkyl groups often have 2 to 24, 4 to 24 carbon atoms,
4 to 20 carbon atoms, or 4 to 12 carbon atoms. Aryl groups often
have 6 to 24 carbon atoms, 6 to 20 carbon atoms, 6 to 12 carbon
atoms, or 6 to 10 carbon atoms. Aralkyl and alkaryl groups often
have an aryl or arylene portion with 6 to 20 carbon atoms, 6 to 12
carbon atoms, or 6 to 10 carbon atoms and an alkyl or alkylene
portion with 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4
carbon atoms.
[0109] In certain embodiments, a shell layer copolymer includes one
or more low Tg (meth)acrylate monomeric units of Formula (II)
derived from monomers such as 2-ethylhexyl (meth)acrylate, ethyl
acrylate, n-butyl acrylate, isobutyl acrylate, hexyl
(meth)acrylate, 2-octyl acrylate, isooctyl acrylate, isononyl
acrylate, isostearyl acrylate, 2-methylbutyl acrylate, and
combinations thereof. In certain embodiments, a shell layer
copolymer includes one or more low Tg (meth)acrylate monomeric
units of Formula (II) derived from monomers selected from the group
of 2-ethylhexyl acrylate, n-butyl acrylate, isooctyl acrylate,
2-octyl acrylate, and combinations thereof. Various isomer mixtures
of the alkyl (meth)acrylates can be used such as those described,
for example, in PCT Patent Application Publication WO 2012/088126
(Clapper et al.).
[0110] In certain embodiments, a shell layer copolymer includes one
or more polar monomeric units derived from polar monomers as
described above for the cushion layer.
[0111] In certain embodiments, a cushion layer (meth)acrylate
copolymer includes one or more polar monomeric units having an acid
group and an adjacent shell layer copolymer includes one or more
polar monomeric units having a basic group. Alternatively, in
certain embodiments, a cushion layer (meth)acrylate copolymer
includes one or more polar monomeric units having a basic group and
an adjacent shell layer copolymer includes one or more polar
monomeric units having an acid group. This complementary
orientation of acid- and base-containing monomeric units can
enhance the adhesion between a cushion layer and a shell layer.
Monomers with basic groups are often nitrogen-containing monomers
such as those with a primary amido group, secondary amido group, or
amino group.
[0112] In certain embodiments, a shell layer copolymer includes one
or more polar monomeric units derived from monomers selected from
the group of (meth)acrylic acid, (meth)acrylamide,
alkyl-substituted (meth)acrylamides (e.g., N,N-dimethyl
acrylamide), and combinations thereof.
[0113] In certain embodiments, a shell layer copolymer includes one
or more high Tg nonpolar monomeric units derived from monomers
selected from the group of styrene, substituted styrene (e.g.,
methyl styrene), isobornyl acrylate, methyl (meth)acrylate,
tert-butyl (meth)acrylate, iso-butyl methacrylate, cyclohexyl
(meth)acrylate, norbornyl (meth)acrylate, and combinations thereof.
In certain embodiments, a shell layer copolymer includes one or
more high Tg nonpolar monomeric units derived from monomers
selected from the group of styrene, isobornyl (meth)acrylate,
norbornyl acrylate, methyl (meth)acrylate, tert-butyl
(meth)acrylate, iso-butyl methacrylate, cyclohexyl (meth)acrylate,
octadecyl acrylate, and combinations thereof.
[0114] One or more other monomeric units may be included in a shell
layer copolymer of the present disclosure.
[0115] In certain embodiments, a shell layer copolymer further
comprises optional monomers such as vinyl acetate monomeric units.
In certain embodiments, such vinyl acetate monomeric units are
present in an amount of up to 7 wt-%, up to 5 wt-%, up to 3-wt-%,
or up to 2 wt-%, based on the total weight of monomeric units in
the copolymer.
[0116] In addition to a copolymer as described herein, in certain
embodiments, a shell layer adhesive further includes one or more
additives selected from the group of colorants (e.g.,
UV-fluorescent molecules), fillers, flame retardants, antioxidants,
UV-stabilizers, viscosity modifiers, and combinations thereof. For
example, antioxidants and/or UV stabilizers such as hydroquinone
monomethyl ether (4-methoxyphenol, MeHQ), and that available under
the trade name IRGANOX 1010
(tetrakis(methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate))metha-
ne) from BASF Corp., can be mixed into the cushion layer
(meth)acrylate copolymer to increase its temperature stability. If
used, an antioxidant and/or stabilizer is typically used in the
range of 0.01 wt-% to 1.0 wt-%, based on the total weight of the
adhesive.
[0117] In certain embodiments, a shell layer adhesive includes
tackifiers and/or plasticizers in a combined amount of no more than
20 wt-%. In certain embodiments, a shell layer adhesive includes
substantially no tackifiers and/or plasticizers. In this context,
"substantially no" means less than 1 wt-%, less than 0.5 wt-%, or
less than 0.1 wt-%, based on the total weight of the adhesive.
[0118] The copolymers and adhesives of the shell layer may be
prepared by any conventional polymerization method (such as
solution polymerization or emulsion polymerization) including
thermal bulk polymerization under adiabatic conditions, as is
disclosed in, for example, U.S. Pat. No. 5,637,646 (Ellis) and U.S.
Pat. No. 5,986,011 (Ellis et al.). Other methods of preparing
(meth)acrylate copolymers include the continuous free radical
polymerization methods described in U.S. Pat. No. 4,619,979
(Kotnour et al.) and U.S. Pat. No. 4,843,134 (Kotnour et al.), the
polymerization within a polymeric package as described in U.S. Pat.
No. 5,804,610 (Hamer et al.), and the on-web polymerization process
as described in U.S. Pat. No. 4,181,752 (Martens et al.).
Alternatively, the copolymers and adhesives of the shell layer may
be prepared as exemplified in the Examples Section.
Backings and Adhesive Articles
[0119] The adhesive articles of the present disclosure may be in
the form of a tape or a die-cut article (e.g., labels, shaped
graphic components).
[0120] Referring to FIG. 1, an adhesive article (e.g., tape) 10
includes a flexible backing 12, a first cushion layer 20
permanently bonded to a first surface 14 of the flexible backing
12, and a first continuous shell layer 22 adjacent the first
cushion layer 20. Such articles can be single-sided adhesive
articles (e.g., tapes or labels). In certain embodiments, such an
adhesive article may further include a low adhesion backsize (a
LAB) (not shown) on a second surface 16 of the flexible backing 12.
A LAB is typically used in a tape on the surface of a backing
opposite the surface on which the adhesive is disposed to allow a
tape to unwind easily. Suitable LAB materials are described, for
example, in U.S. Pat. No. 6,919,405 (Kinning et al.).
[0121] Alternatively, in certain embodiments, an adhesive article
of the present disclosure includes a second cushion layer
permanently bonded to a second surface (i.e., second side) of the
flexible backing, and a second continuous shell layer adjacent the
second cushion layer. Such double-sided adhesive articles (e.g.,
tapes) may further include a release liner disposed on one of the
first shell layer and/or the second shell layer. Release liners,
which are removed before use of the adhesive article, include any
suitable flexible material without specific limitations. Suitable
release liners are commercially available and well known to one of
skill in the art.
[0122] The flexible backings of the present disclosure may be any
of a wide variety that are typically used in adhesive articles,
particularly adhesive tapes. In certain embodiments, a flexible
backing includes a material selected from the group of paper (e.g.,
Kraft paper) and polymeric films (e.g., polypropylene,
polyethylene, polyurethane, polyester (e.g., polyethylene
tereplithalate), ethylene vinyl acetate, polyvinyl chloride
(vinyl), cellulose acetate, and ethyl cellulose). The backing
materials can be in the form of a nonwoven web, extruded film,
metal foil or sheet backing (for example, retro-reflective or
graphic film sheets).
[0123] Various well-known techniques of applying the cushion and
shell layers can be used, including various wet coating methods
(direct or indirect) and dry laminating methods, although dry
laminating methods may not be as desirable as wet coating methods
(e.g., knife coating, roll coating, gravure coating, rod coating,
curtain coating, and air knife coating).
[0124] Every interface in an adhesive article is a potential
failure interface which can diminish the ultimate potential
strength of the adhesive bond. By utilizing the complementary
orientation of acid- and base-containing monomeric units in the
cushion and shell layers as described above, it is possible to
enhance the interfacial bond between these layers to reduce or
eliminate the possibility of bond failure at this two-layer
interface. In other embodiments, techniques to enhance this bond
include e-beam crosslinking the total tape construction after both
layers are applied to a backing, UV post-curing the adhesives to
directly crosslink the cushion and shell layers, and directly
polymerizing one layer on top of the other to promote
interpenetrating networks at the two-layer interface.
[0125] In still other embodiments, a cushion layer and/or shell
layer comprises a surface treatment (e.g., plasma treatment, corona
treatment, or chemical primer) to enhance adhesion to each other.
Thus, the cushion layer and the shell layer may be separated by one
or more other materials, such as a chemical primer layer.
Alternatively, in certain embodiments, a shell layer is directly
disposed on a cushion layer (e.g., without a chemical primer). In
certain embodiments, a surface of the flexible backing includes a
surface treatment (e.g., plasma treatment, corona treatment, or
chemical primer) to enhance adhesion of a cushion layer. Thus, the
flexible backing and the cushion layer may be separated by one or
more other materials, such as a chemical primer layer.
Alternatively, in certain embodiments, a cushion layer is directly
disposed on a surface of the flexible backing (e.g., without a
chemical primer). Suitable surface treatments are well known to
those skilled in the art and include coronas, plasmas, and flames,
as described, for example in U.S. Pat. No. 4,828,871 (Strobel; PSA
adhesion improved by plasma) and International Pub. No. WO
2012/152710 (Tesa; PSA adhesion improved by corona or flame).
[0126] Various combinations of these techniques can be used if
desired to enhance adhesion between a cushion layer and a shell
layer or between a flexible backing and a cushion layer.
Embodiments
[0127] Embodiment 1 is an adhesive article comprising:
[0128] a flexible backing;
[0129] a first cushion layer permanently bonded to a first surface
of the flexible backing, wherein the first cushion layer: [0130]
has an average thickness of at least 10 micrometers; and [0131]
comprises an acrylate pressure-sensitive adhesive having a Fox Tg
of up to -30.degree. C., wherein the acrylate pressure-sensitive
adhesive comprises a (meth)acrylate copolymer comprising: [0132] a)
one or more (meth)acrylate monomeric units of Formula (I) in an
amount of at least 60 wt-% (or at least 65 wt-%, or at least 70
wt-%, at least 75 wt-%, or at least 80 wt-%), based on a total
weight of monomeric units in the (meth)acrylate copolymer:
[0132] ##STR00005## [0133] wherein: [0134] R.sub.1 is hydrogen or a
methyl group; and [0135] R.sub.2 is an alkyl, heteroalkyl, aryl,
aralkyl, or alkaryl group; with the proviso that the first
monomeric unit of Formula (I) with R.sub.2 having at least 8 carbon
atoms is present in an amount of at least 20 wt-% (or at least 30
wt-%, or at least 40 wt-%), based on a total weight of monomeric
units in the (meth)acrylate copolymer; and [0136] b) one or more
polar monomeric units in an amount of up to 7 wt-% (or up to 6
wt-%, or up to 5 wt-%, or up to 4 wt-%), based on a total weight of
monomeric units in the (meth)acrylate copolymer; [0137] wherein the
sum of all monomeric units of the first cushion layer
(meth)acrylate copolymer equals 100% by weight; and
[0138] a first continuous shell layer adjacent the first cushion
layer, wherein: [0139] the first continuous shell layer has an
average thickness of up to 25 micrometers; [0140] the ratio of the
first cushion layer average thickness to the first shell layer
average thickness is at least 2:1; [0141] the first continuous
shell layer comprises an adhesive (in certain embodiments, the
adhesive is a pressure-sensitive adhesive) having a Fox Tg of
-20.degree. C. to +50.degree. C.; and [0142] the first continuous
shell layer adhesive comprises a copolymer having a weight average
molecular weight of at least 100,000 Daltons, wherein the copolymer
comprises: [0143] a) one or more low Tg (meth)acrylate monomeric
units of Formula (II) in an amount of at least 25 wt-% (or at least
30 wt-%, or at least 35 wt-%, or at least 40 wt-%), based on a
total weight of monomeric units in the copolymer:
[0143] ##STR00006## [0144] wherein: [0145] R.sub.1 is hydrogen or a
methyl group; and [0146] R.sub.3 is an alkyl, heteroalkyl, aryl,
aralkyl, or alkaryl group; [0147] b) one or more polar monomeric
units in an amount of up to 5 wt-% (or up to 4.5 wt-%, or up to 4
wt-%, or up to 3.5 wt-%), based on a total weight of monomeric
units in the copolymer; and [0148] c) one or more high Tg nonpolar
monomeric units in an amount of at least 35 wt-% (or at least 40
wt-%, or at least 45 wt-%, or at least 50 wt-%), based on a total
weight of monomeric units in the copolymer; [0149] wherein the sum
of all monomeric units of the first shell layer copolymer equals
100% by weight.
[0150] Embodiment 2 is the adhesive article of embodiment 1 wherein
the acrylate pressure-sensitive adhesive of the first cushion layer
has a Fox Tg of at least -85.degree. C.
[0151] Embodiment 3 is the adhesive article of embodiment 1 or 2
wherein the first cushion layer has an average thickness of up to
150 micrometers (or up to 100 micrometers, or up to 50
micrometers).
[0152] Embodiment 4 is the adhesive article of any one of the
previous embodiments wherein the first shell layer has an average
thickness of up to 20 micrometers (or up to 12 micrometers, or up
to 10 micrometers, or up to 8 micrometers, or up to 6 micrometers,
or up to 4 micrometers, or up to 2 micrometers).
[0153] Embodiment 5 is the adhesive article of any one of the
previous embodiments wherein the ratio of the first cushion layer
average thickness to the first shell layer average thickness is at
least 3:1 (or at least 4:1, or at least 5:1, or at least 10:1, or
at least 20:1, or at least 50:1, or at least 70:1).
[0154] Embodiment 6 is the adhesive article of any one of the
previous embodiments wherein the ratio of the first cushion layer
average thickness to the first shell layer average thickness is up
to 300:1 (or up to 200:1, or up to 100:1).
[0155] Embodiment 7 is the adhesive article of any one of the
previous embodiments wherein the adhesive of the first shell layer
has a Fox Tg of up to +40.degree. C. (or up to +30.degree. C., or
up to +20.degree. C.).
[0156] Embodiment 8 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer comprises one or more (meth)acrylate monomeric units of
Formula (I) in an amount of up to 99.5 wt-% (or up to 95 wt-%, or
up to 90 wt-%, or up to 85 wt-%), based on a total weight of
monomeric units in the (meth)acrylate copolymer.
[0157] Embodiment 9 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer comprises one or more polar monomeric units in an amount
of at least 0.5 wt-% (or at least 1 wt-%, or at least 1.5 wt-%, or
at least 2 wt-%, or at least 2.5 wt-%, or at least 3 wt-%), based
on a total weight of monomeric units in the (meth)acrylate
copolymer.
[0158] Embodiment 10 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer comprises one or more (meth)acrylate monomeric units of
Formula (I) wherein R.sub.2 is an alkyl group having 1 to 24 carbon
atoms.
[0159] Embodiment 11 is the adhesive article of embodiment 10
wherein the first cushion layer (meth)acrylate copolymer comprises
one or more (meth)acrylate monomeric units of Formula (I) derived
from monomers selected from the group of 2-ethylhexyl
(meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate,
n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl
(meth)acrylate, hexyl (meth)acrylate, 2-octyl (meth)acrylate,
isooctyl (meth)acrylate, isononyl (meth)acrylate, isobornyl
(meth)acrylate, norbornyl (meth)acrylate, isostearyl
(meth)acrylate, behenyl (meth)acrylate, 2-methylbutyl
(meth)acrylate, and combinations thereof (in certain embodiments,
these monomers are selected from the group of 2-ethylhexyl
acrylate, n-butyl acrylate, isooctyl acrylate, 2-octyl acrylate,
and combinations thereof).
[0160] Embodiment 12 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer comprises one or more polar monomeric units derived from
monomers selected from the group of (meth)acrylic acid,
(meth)acrylamide, alkyl-substituted (meth)acrylamides (e.g.,
N,N-dimethyl acrylamide), and combinations thereof.
[0161] Embodiment 13 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
comprises one or more low Tg (meth)acrylate monomeric units of
Formula (I) in an amount of up to 64.5 wt-% (or up to 60 wt-%, or
up to 55 wt-%, or up to 50 wt-%), based on a total weight of
monomeric units in the copolymer.
[0162] Embodiment 14 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
comprises one or more polar monomeric units in an amount of at
least 0.5 wt-% (or at least 1 wt-%, or at least 1.5 wt-%, or at
least 2 wt-%), based on a total weight of monomeric units in the
copolymer.
[0163] Embodiment 15 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
comprises one or more high Tg nonpolar monomeric units in an amount
of up to 74.5 wt-% (or up to 70 wt-%, or up to 65 wt-%, or up to 60
wt-%), based on a total weight of monomeric units in the
copolymer.
[0164] Embodiment 16 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
comprises one or more low Tg (meth)acrylate monomeric units of
Formula (II) wherein R.sub.3 is an alkyl group having 2 to 24
carbon atoms (in certain embodiments, 4 to 24 carbon atoms).
[0165] Embodiment 17 is the adhesive article of embodiment 16
wherein the first shell layer copolymer comprises one or more low
Tg (meth)acrylate monomeric units of Formula (II) derived from
monomers selected from the group of 2-ethylhexyl (meth)acrylate,
ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl
(meth)acrylate, 2-octyl acrylate, isooctyl acrylate, isononyl
acrylate, isostearyl acrylate, 2-methylbutyl acrylate, and
combinations thereof (in certain embodiments, these monomers are
selected from the group of 2-ethylhexyl acrylate, n-butyl acrylate,
isooctyl acrylate, 2-octyl acrylate, and combinations thereof).
[0166] Embodiment 18 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
comprises one or more polar monomeric units derived from monomers
selected from the group of (meth)acrylic acid, (meth)acrylamide,
alkyl-substituted (meth)acrylamides (e.g., N,N-dimethyl
acrylamide), and combinations thereof.
[0167] Embodiment 19 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
comprises one or more high Tg nonpolar monomeric units derived from
monomers selected from the group of styrene, substituted styrene
(e.g., methyl styrene), isobornyl acrylate, methyl (meth)acrylate,
tert-butyl (meth)acrylate, iso-butyl methacrylate, cyclohexyl
(meth)acrylate, norbornyl (meth)acrylate, and combinations thereof
(in certain embodiments, these monomers are selected from the group
of styrene, isobornyl (meth)acrylate, norbornyl acrylate, methyl
(meth)acrylate, tert-butyl (meth)acrylate, iso-butyl methacrylate,
cyclohexyl (meth)acrylate, and combinations thereof).
[0168] Embodiment 20 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer further comprises vinyl acetate monomeric units in an
amount of up to 7 wt-%, based on the total weight of monomeric
units in the copolymer.
[0169] Embodiment 21 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer
further comprises vinyl acetate monomeric units in an amount of up
to 7 wt-%, based on the total weight of monomeric units in the
copolymer.
[0170] Embodiment 22 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer comprises one or more polar monomeric units having an
acid group and the first shell layer copolymer comprises one or
more polar monomeric units having a basic group.
[0171] Embodiment 23 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer comprises one or more polar monomeric units having a
basic group and the first shell layer copolymer comprises one or
more polar monomeric units having an acidic group.
[0172] Embodiment 24 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer has a weight average molecular weight of at least 100,000
Daltons (or at least 200,000 Daltons, or at least 400,000
Daltons).
[0173] Embodiment 25 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer (meth)acrylate
copolymer has a weight average molecular weight of up to 2,000,000
Daltons (or up to 1,000,000 Daltons, or up to 700,000 Daltons, or
up to 500,000 Daltons).
[0174] Embodiment 26 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer has a
weight average molecular weight of up to 2,000,000 Daltons (or up
to 1,000,000 Daltons, or up to 700,000 Daltons, or up to 500,000
Daltons).
[0175] Embodiment 27 is the adhesive article of any one of the
previous embodiments wherein the first shell layer copolymer has a
weight average molecular weight of at least 200,000 Daltons (or at
least 300,000 Daltons, or at least 400,000 Daltons).
[0176] Embodiment 28 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer acrylate
pressure-sensitive adhesive further comprises one or more additives
selected from the group of colorants, fillers, flame retardants,
antioxidants, UV-stabilizers, viscosity modifiers, and combinations
thereof.
[0177] Embodiment 29 is the adhesive article of any one of the
previous embodiments wherein the first shell layer adhesive further
comprises one or more additives selected from the group of
colorants (e.g., UV-fluorescent molecules), fillers, flame
retardants, antioxidants, UV-stabilizers, viscosity modifiers, and
combinations thereof.
[0178] Embodiment 30 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer acrylate
pressure-sensitive adhesive includes tackifiers and/or plasticizers
in a combined amount of no more than 20 wt-%.
[0179] Embodiment 31 is the adhesive article of embodiment 30
wherein the first cushion layer acrylate pressure-sensitive
adhesive includes substantially no tackifiers and/or
plasticizers.
[0180] Embodiment 32 is the adhesive article of any one of the
previous embodiments wherein the first shell layer adhesive
includes tackifiers and/or plasticizers in a combined amount of no
more than 20 wt-0.
[0181] Embodiment 33 is the adhesive article of embodiment 32
wherein the first shell layer adhesive includes substantially no
tackifiers and/or plasticizers.
[0182] Embodiment 34 is the adhesive article of any one of the
previous embodiments wherein the flexible backing comprises a
material selected from the group of paper (e.g., Kraft paper) and
polymeric films (e.g., polypropylene, polyethylene, polyurethane,
polyester (e.g., polyethylene terephthalate), ethylene vinyl
acetate, cellulose acetate, and ethyl cellulose).
[0183] Embodiment 35 is the adhesive article of any one of the
previous embodiments wherein the first surface of the flexible
backing comprises a surface treatment (e.g., plasma treatment,
corona treatment, or chemical primer).
[0184] Embodiment 36 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer is directly
disposed on the first surface of the flexible backing (e.g.,
without a chemical primer).
[0185] Embodiment 37 is the adhesive article of any one of the
previous embodiments wherein the first cushion layer comprises a
surface treatment (e.g., plasma treatment, corona treatment, or
chemical primer).
[0186] Embodiment 38 is the adhesive article of any one of the
previous embodiments wherein the first shell layer is directly
disposed on the first cushion layer (e.g., without a chemical
primer).
[0187] Embodiment 39 is the adhesive article of any one of
embodiments 1 through 38 which is a die-cut article.
[0188] Embodiment 40 is the adhesive article of any one of
embodiments 1 through 38 which is a tape.
[0189] Embodiment 41 is the adhesive article of any one of the
previous embodiments which demonstrates an increase (in certain
embodiments, at least a two-fold increase, or at least a three-fold
increase) in 180.degree. angle peel adhesion strength at a peel
rate of 0.2 inch/minute (0.08 millimeter/second) from stainless
steel at room temperature compared to an adhesive article having
the same flexible backing and first cushion layer but without the
first shell layer.
[0190] Embodiment 42 is the adhesive article of any one of the
previous embodiments which demonstrates an increase (in certain
embodiments, at least a two-fold increase, or at least a three-fold
increase) in 180.degree. angle peel adhesion strength at a peel
rate of 0.2 inch/minute (0.08 millimeter/second) from stainless
steel or polypropylene at a temperature of up to 65.degree. C.
compared to an adhesive article having the same flexible backing
and first cushion layer but without the first shell layer.
[0191] Embodiment 43 is the adhesive article of embodiment 41 or 42
which demonstrates an average rolling ball stopping distance
according to a Rolling Ball Tack Test of at least 200 mm (or at
least 300 mm, or at least 400 mm).
[0192] Embodiment 44 is the adhesive article of any one of the
previous embodiments further comprising an LAB on a second surface
of the flexible backing.
[0193] Embodiment 45 is the adhesive article of any one of
embodiments 1 through 43 further comprising:
[0194] a second cushion layer permanently bonded to a second
surface of the flexible backing, wherein the second cushion: [0195]
has an average thickness of at least 10 micrometers; and [0196]
comprises an acrylate pressure-sensitive adhesive having a Fox Tg
of up to -30.degree. C., wherein the acrylate pressure-sensitive
adhesive comprises a (meth)acrylate copolymer comprising: [0197] a)
one or more (meth)acrylate monomeric units of Formula (I) in an
amount of at least 60 wt-% (or at least 65 wt-%, or at least 70
wt-%, or at least 75 wt-%, or at least 80 wt-%), based on a total
weight of monomeric units in the (meth)acrylate copolymer:
[0197] ##STR00007## [0198] wherein: [0199] R.sub.1 is hydrogen or a
methyl group; and [0200] R.sub.2 is an alkyl, heteroalkyl, aryl,
aralkyl, or alkaryl group; with the proviso that the second
monomeric unit of Formula (I) with R.sub.2 having at least 8 carbon
atoms is present in an amount of at least 20 wt-% (or at least 30
wt-%, or at least 40 wt-%), based on a total weight of monomeric
units in the (meth)acrylate copolymer; and [0201] b) one or more
polar monomeric units in an amount of up to 7 wt-% (or up to 6
wt-%, or up to 5 wt-%, or up to 4 wt-%), based on a total weight of
monomeric units in the (meth)acrylate copolymer; [0202] wherein the
sum of all monomeric units of the second cushion layer
(meth)acrylate copolymer equals 100% by weight; and a second
continuous shell layer adjacent the second cushion layer, wherein:
[0203] the second continuous shell layer has an average thickness
of up to 25 micrometers; [0204] the ratio of the second cushion
layer average thickness to the second shell layer average thickness
is at least 2:1; [0205] the second continuous shell layer comprises
an adhesive (in certain embodiments, the adhesive is a
pressure-sensitive adhesive) having a Fox Tg of -20.degree. C. to
+50.degree. C.; and [0206] the second continuous shell layer
adhesive comprises a copolymer having a weight average molecular
weight of at least 100,000 Daltons, wherein the copolymer
comprises: [0207] a) one or more low Tg (meth)acrylate monomeric
units of Formula (II) in an amount of at least 25 wt-% (or at least
30 wt-%, or at least 35 wt-%, or at least 40 wt-%), based on a
total weight of monomeric units in the copolymer:
[0207] ##STR00008## [0208] wherein: [0209] R.sub.1 is hydrogen or a
methyl group; and [0210] R.sub.3 is an alkyl, heteroalkyl, aryl,
aralkyl, or alkaryl group; [0211] b) one or more polar monomeric
units in an amount of up to 5 wt-%, based on a total weight of
monomeric units in the copolymer; and [0212] c) one or more high Tg
nonpolar monomeric units in an amount of at least 35 wt-% (or at
least 40 wt-%, or at least 45 wt-%, or at least 50 wt-%), based on
a total weight of monomeric units in the copolymer; [0213] wherein
the sum of all monomeric units of the second shell layer copolymer
equals 100% by weight.
[0214] Embodiment 46 is the adhesive article of embodiment 45
further comprising a release liner disposed on one of the first
shell layer and/or the second shell layer.
[0215] Embodiment 47 is the adhesive article of embodiment 45 or 46
wherein the acrylate pressure-sensitive adhesive of the second
cushion layer has a Fox Tg of at least -85.degree. C.
[0216] Embodiment 48 is the adhesive article of any one of
embodiments 45 through 47 wherein the second cushion layer has an
average thickness of up to 150 micrometers (or up to 100
micrometers, or up to 50 micrometers).
[0217] Embodiment 49 is the adhesive article of any one of
embodiments 45 through 48 wherein the second shell layer has an
average thickness of up to 20 micrometers (or up to 12 micrometers,
or up to 10 micrometers, or up to 8 micrometers, or up to 6
micrometers, or up to 4 micrometers, or up to 2 micrometers).
[0218] Embodiment 50 is the adhesive article of any one of
embodiments 45 through 49 wherein the ratio of the second cushion
layer average thickness to the second shell layer average thickness
is at least 3:1 (or at least 4:1, or at least 5:1, or at least
10:1, or at least 20:1, or at least 50:1, or at least 70:1).
[0219] Embodiment 51 is the adhesive article of any one of
embodiments 45 through 50 wherein the ratio of the second cushion
layer average thickness to the second shell layer average thickness
is up to 300:1 (or up to 200:1, or up to 100:1).
[0220] Embodiment 52 is the adhesive article of any one of
embodiments 45 through 51 wherein the adhesive of the second shell
layer has a Fox Tg of up to +40.degree. C. (or up to +30.degree.
C., or up to +20.degree. C.).
[0221] Embodiment 53 is the adhesive article of any one of
embodiments 45 through 52 wherein the second cushion layer
(meth)acrylate copolymer comprises one or more (meth)acrylate
monomeric units of Formula (I) in an amount of up to 99.5 wt-% (or
up to 95 wt-%, or up to 90 wt-%, or up to 85 wt-%), based on a
total weight of monomeric units in the (meth)acrylate
copolymer.
[0222] Embodiment 54 is the adhesive article of any one of
embodiments 45 through 53 wherein the second cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units in an amount of at least 0.5 wt-% (or at least 1 wt-%, at
least 1.5 wt-%, at least 2 wt-%, at least 2.5 wt-%, or at least 3
wt-%), based on a total weight of monomeric units in the
(meth)acrylate copolymer.
[0223] Embodiment 55 is the adhesive article of any one of
embodiments 45 through 54 wherein the second cushion layer
(meth)acrylate copolymer comprises one or more (meth)acrylate
monomeric units of Formula (I) wherein R.sub.2 is an alkyl group
having 1 to 24 carbon atoms.
[0224] Embodiment 56 is the adhesive article of embodiment 55
wherein the second cushion layer (meth)acrylate copolymer comprises
one or more (meth)acrylate monomeric units of Formula (I) derived
from monomers selected from the group of 2-ethylhexyl
(meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate,
n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl
(meth)acrylate, hexyl (meth)acrylate, 2-octyl (meth)acrylate,
isooctyl (meth)acrylate, isononyl (meth)acrylate, isobornyl
(meth)acrylate, norbornyl (meth)acrylate, isostearyl
(meth)acrylate, behenyl (meth)acrylate, 2-methylbutyl
(meth)acrylate, and combinations thereof (in certain embodiments,
these monomers are selected from the group of 2-ethylhexyl
acrylate, n-butyl acrylate, isooctyl acrylate, 2-octyl acrylate,
and combinations thereof).
[0225] Embodiment 57 is the adhesive article of any one of
embodiments 45 through 56 wherein the second cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units derived from monomers selected from the group of
(meth)acrylic acid, (meth)acrylamide, alkyl-substituted
(meth)acrylamides (e.g., N,N-dimethyl acrylamide), and combinations
thereof.
[0226] Embodiment 58 is the adhesive article of any one of
embodiments 45 through 57 wherein the second shell layer copolymer
comprises one or more low Tg (meth)acrylate monomeric units of
Formula (II) in an amount of up to 64.5 wt-% (or up to 60 wt-%, or
up to 55 wt-%, or up to 50 wt-%), based on a total weight of
monomeric units in the copolymer.
[0227] Embodiment 59 is the adhesive article of any one of
embodiments 45 through 58 wherein the second shell layer copolymer
comprises one or more polar monomeric units in an amount of at
least 0.5 wt-% (or at least 1 wt-%, or at least 1.5 wt-%, or at
least 2 wt-%), based on a total weight of monomeric units in the
copolymer.
[0228] Embodiment 60 is the adhesive article of any one of
embodiments 45 through 59 wherein the second shell layer copolymer
comprises one or more high Tg nonpolar monomeric units in an amount
of up to 74.5 wt-% (or up to 70 wt-%, or up to 65 wt-%, or up to 60
wt-%), based on a total weight of monomeric units in the
copolymer.
[0229] Embodiment 61 is the adhesive article of any one of
embodiments 45 through 60 wherein the second shell layer copolymer
comprises one or more low Tg (meth)acrylate monomeric units of
Formula (II) wherein R.sub.3 is an alkyl group having 2 to 24
carbon atoms (in certain embodiments, 4 to 24 carbon atoms).
[0230] Embodiment 62 is the adhesive article of embodiment 61
wherein the second shell layer copolymer comprises one or more low
Tg (meth)acrylate monomeric units of Formula (II) derived from
monomers selected from the group of 2-ethylhexyl (meth)acrylate,
ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl
(meth)acrylate, 2-octyl acrylate, isooctyl acrylate, isononyl
acrylate, isostearyl acrylate, 2-methylbutyl acrylate, and
combinations thereof (in certain embodiments, 2-ethylhexyl
acrylate, n-butyl acrylate, isooctyl acrylate, 2-octyl acrylate,
and combinations thereof).
[0231] Embodiment 63 is the adhesive article of any one of
embodiments 45 through 62 wherein the second shell layer copolymer
comprises one or more polar monomeric units derived from monomers
selected from the group of (meth)acrylic acid, (meth)acrylamide,
alkyl-substituted (meth)acrylamides (e.g., N,N-dimethyl
acrylamide), and combinations thereof.
[0232] Embodiment 64 is the adhesive article of any one of
embodiments 45 through 63 wherein the second shell layer copolymer
comprises one or more high Tg nonpolar monomeric units derived from
monomers selected from the group of styrene, substituted styrene
(e.g., methyl styrene), isobornyl acrylate, methyl (meth)acrylate,
tert-butyl (meth)acrylate, iso-butyl methacrylate, cyclohexyl
(meth)acrylate, norbornyl (meth)acrylate, and combinations thereof
(in certain embodiments, these monomers are selected from the group
of styrene, isobornyl (meth)acrylate, norbornyl acrylate, methyl
(meth)acrylate, tert-butyl (meth)acrylate, iso-butyl methacrylate,
cyclohexyl (meth)acrylate, and combinations thereof).
[0233] Embodiment 65 is the adhesive article of any one of
embodiments 45 through 64 wherein the second cushion layer
(meth)acrylate copolymer further comprises vinyl acetate monomeric
units in an amount of up to 7 wt-%, based on the total weight of
monomeric units in the copolymer.
[0234] Embodiment 66 is the adhesive article of any one of
embodiments 45 through 65 wherein the second shell layer copolymer
further comprises vinyl acetate monomeric units in an amount of up
to 7 wt-%, based on the total weight of monomeric units in the
copolymer.
[0235] Embodiment 67 is the adhesive article of any one of
embodiments 45 through 66 wherein the second cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units having an acid group and the second shell layer copolymer
comprises one or more polar monomeric units having a basic
group.
[0236] Embodiment 68 is the adhesive article of any one of
embodiments 45 through 67 wherein the second cushion layer
(meth)acrylate copolymer comprises one or more polar monomeric
units having a basic group and the second shell layer copolymer
comprises one or more polar monomeric units having an acidic
group.
[0237] Embodiment 69 is the adhesive article of any one of
embodiments 45 through 68 wherein the second cushion layer
(meth)acrylate copolymer has a weight average molecular weight of
at least 100,000 Daltons (or at least 200,000 Daltons, or at least
400,000 Daltons).
[0238] Embodiment 70 is the adhesive article of any one of
embodiments 45 through 69 wherein the second cushion layer
(meth)acrylate copolymer has a weight average molecular weight of
up to 2,000,000 Daltons (or up to 1,000,000 Daltons, or up to
700,000 Daltons, or up to 500,000 Daltons).
[0239] Embodiment 71 is the adhesive article of any one of
embodiments 45 through 70 wherein the second shell layer copolymer
has a weight average molecular weight of up to 2,000,000 Daltons
(or up to 1,000,000 Daltons, or up to 700,000 Daltons, or up to
500,000 Daltons).
[0240] Embodiment 72 is the adhesive article of any one of
embodiments 45 through 71 wherein the second shell layer copolymer
has a weight average molecular weight of at least 200,000 Daltons
(or at least 300,000 Daltons, or at least 400,000 Daltons).
[0241] Embodiment 73 is the adhesive article of any one of
embodiments 45 through 72 wherein the second cushion layer acrylate
pressure-sensitive adhesive further comprises one or more additives
selected from the group of colorants, fillers, flame retardants,
antioxidants, UV-stabilizers, viscosity modifiers, and combinations
thereof.
[0242] Embodiment 74 is the adhesive article of any one of
embodiments 45 through 73 wherein the second shell layer adhesive
further comprises one or more additives selected from the group of
colorants (e.g., UV-fluorescent molecules), fillers, flame
retardants, antioxidants, UV-stabilizers, viscosity modifiers, and
combinations thereof.
[0243] Embodiment 75 is the adhesive article of any one of
embodiments 45 through 74 wherein the second cushion layer acrylate
pressure-sensitive adhesive includes tackifiers and/or plasticizers
in a combined amount of no more than 20 wt-%.
[0244] Embodiment 76 is the adhesive article of embodiment 75
wherein the second cushion layer acrylate pressure-sensitive
adhesive includes substantially no tackifiers and/or
plasticizers.
[0245] Embodiment 77 is the adhesive article of any one of
embodiments 45 through 76 wherein the second shell layer adhesive
includes tackifiers and/or plasticizers in a combined amount of no
more than 20 wt-%.
[0246] Embodiment 78 is the adhesive article of embodiment 77
wherein the second shell layer adhesive includes substantially no
tackifiers and/or plasticizers.
[0247] Embodiment 79 is the adhesive article of any one of
embodiments 45 through 78 wherein the second cushion layer is
directly disposed on the second surface of the flexible backing
(e.g., without a chemical primer).
[0248] Embodiment 80 is the adhesive article of any one of
embodiments 45 through 79 wherein the second cushion layer
comprises a surface treatment (e.g., plasma treatment, corona
treatment, or chemical primer).
[0249] Embodiment 81 is the adhesive article of any one of
embodiments 45 through 80 wherein the second shell layer is
directly disposed on the second cushion layer (e.g., without a
chemical primer).
[0250] Embodiment 82 is the adhesive article of any one of
embodiments 45 through 81 which demonstrates an increase (in
certain embodiments, at least a two-fold increase, or at least a
three-fold increase) in 180.degree. angle peel adhesion strength at
a peel rate of 0.2 inch/minute (0.08 millimeter/second) from
stainless steel at room temperature compared to an adhesive article
having the same flexible backing and second cushion layer but
without the second shell layer.
[0251] Embodiment 83 is the adhesive article of embodiment 82 which
demonstrates an increase (in certain embodiments, at least a
two-fold increase, or at least a three-fold increase) in
180.degree. angle peel adhesion strength at a peel rate of 0.2
inch/minute (0.08 millimeter/second) from stainless steel or
polypropylene at a temperature of up to 65.degree. C. compared to
an adhesive article having the same flexible backing and second
cushion layer but without the second shell layer.
[0252] Embodiment 84 is the adhesive article of embodiment 82 or 83
which demonstrates an average rolling ball stopping distance
according to a Rolling Ball Tack Test of at least 200 mm (or at
least 300 mm, or at least 400 mm).
Examples
[0253] Objects and advantages of this disclosure are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this disclosure.
[0254] Unless otherwise noted, all parts, percentages, ratios, etc.
in the examples and the rest of the specification are by weight,
and all reagents used in the examples were obtained, or are
available, from general chemical suppliers such as, for example,
Sigma-Aldrich, Saint Louis, Mo., or may be synthesized by
conventional methods. The following abbreviations may be used in
this section: mL=milliliter, sec=seconds, min=minutes, h=hours,
g=gram, mg=milligram, mmol=millimole, .degree. C.=degrees Celsius,
.degree. F.=degrees Fahrenheit.
Materials
TABLE-US-00001 [0255] Designator Description IOA Isooctyl acrylate,
a monomer, obtained from 3M (St. Paul, MN, USA). 2EHA 2-ethylhexyl
acrylate, a monomer, available from Sigma- Aldrich, St. Louis, MO.
IBOA Isobornyl acrylate, a monomer, available from Sigma- Aldrich,
St. Louis, MO. AA Acrylic acid, a monomer, available from
Sigma-Aldrich, St. Louis, MO. ACM Acrylamide, a monomer, available
from Zibo Xinye Chemical Company, Limited, Zibo City, Shandong
Province, China. NNDMA N,N-dimethyl acrylamide, a monomer,
available from Sigma-Aldrich, St. Louis, MO. VAZO 52
2,2'-azobis(2,4-dimethylpentanenitrile), a thermally activated
polymerization initiator, available under the trade designation
VAZO 52 from The Chemours Company, Wilmington, DE. VAZO 67
2,2'-azobis(2-methylbutanenitrile), a thermally activated
polymerization initiator, available under the trade designation
VAZO 67 from The Chemours Company, Wilmington, DE. IOTG Iso-octyl
thioglycolate, a chain transfer agent, available from Evans
Chemetics, Teaneck, NJ. TDDM Tertiary dodecyl mercaptan, a chain
transfer agent, available from Sigma-Aldrich, St. Louis, MO. PPET A
polyester terephthalate film having a thickness of 0.002 inch (51
micrometers), primed on one side with a plasma treatment and having
a release coating on the opposite side.
Test Methods
Peel Adhesion Strength
[0256] Peel adhesion strength was measured at various peel rates on
the tapes prepared as described below. Stainless steel and
polypropylene test panels, measuring 2 inches (5.1 centimeters)
wide by 6 inches (15.2 centimeters) long were cleaned by wiping
once with 2-butanone, once with heptane, and three times with
acetone, all using a lint free tissue. The test panels were then
allowed to dry at least 10 minutes before use. Adhesive tape
specimens measuring 1 inch (2.54 centimeters) wide by between 6
inches (15.2 centimeters) to 7 inches (17.8 centimeters) long were
applied to the panels then rolled down using a 2 kilogram (4.5
pound) hard rubber roller back and forth two times over the adhered
tape specimens. To the free end of the adhesive tape was attached a
strip of polyester backed PSA tape (3M 8403 HD, 3M Company, St.
Paul, Minn.) measuring approximately 15 inches (38.1 centimeters)
long which was folded back on itself to create a leader
approximately 7 inches (17.8 centimeters) long. The test panel with
tape specimen attached thereto was conditioned at 65.degree. C. for
24 hours, and then equilibrated at 24.degree. C. and 50% relative
humidity for at least 16 hours prior to testing. Next, the test
panel/tape specimen was secured in the lower grip of a tensile
tester (Model 3365 Dual Column Table Frame, obtained from Instron,
Norwood, Mass.) equipped with a 500 Newton load cell, and the tape
leader was folded back and secured in the top grip to form a
180.degree. peel angle. The tensile tester was programmed to
automatically step through the various peel rates on a single tape
specimen. Peel force was measured across 8 logarithmic peel rate
steps from 8.47 millimeters per second (mm/sec) to 0.00847 mm/sec.
The data acquisition rate was 10 data points per second. At each
peel rate, the peel force was measured for a set acquisition time
and the reported value is the average over the acquisition time.
The first and last 10% of collected data points were not included
in the calculation for each acquisition time.
TABLE-US-00002 Peel Rate (millimeters/second) Acquisition Time
(seconds) 8.47 4.5 0.847 11.3 0.0847 37.5 0.00847 150
[0257] The tensile tester was also equipped with a temperature
control chamber (Model 3119-609, obtained from Instron, Norwood,
Mass.) to allow testing at temperatures other than room
temperature. When using the environmental chamber, test specimens
were equilibrated in the chamber for at least 10 minutes prior to
testing. The results were reported in Newtons/centimeter
(N/cm).
Rolling Ball Tack
[0258] Tack was evaluated using a rolling ball tack test according
to ASTM D3121-17, with the following modifications. The tape
specimens were not conditioned in a humidity controlled environment
prior to testing. The tape specimens were held in place with a
strip of double-sided pressure sensitive adhesive tape (3M 665, 89
micrometers total thickness, 3M Company, St. Paul, Minn.) running
the length of the specimen between the tape backing and the flat
aluminum plate used as the work surface for testing. Chrome plated
steel ball bearings conforming to ASTM A295/A295M-14 and measuring
11 millimeters in diameter and weighing 5.593+/-.003 grams were
used. A RBT-100 rolling ball tack test ramp from Cheminstruments
(Fairfield, Ohio) was employed. The rolling ball distance was taken
as the average of four tests run on a single tape specimen.
Shell Layer Thickness
[0259] Tape specimens were embedded in STRUERS SPECIFIX 20 EPOXY
(Struers, Cleveland, Ohio) and cross-section samples were cut
perpendicular to the tape surface via cryomicrotomy at -30.degree.
C. Tapping Mode Atomic Force Microscopy (AFM) was performed on the
cross-section samples. The contrast between the low glass
transition temperature cushion layer and the high glass transition
shell layer in the tapping mode AFM phase image allowed direct
measurement of the shell layer thicknesses.
Gel Permeation Chromatography (GPC)
[0260] The molecular weight distribution of the compounds was
characterized using conventional gel permeation chromatography
(GPC). The GPC instrumentation, which was obtained from Waters
Corporation (Milford, Mass., USA), included a high pressure liquid
chromatography pump (Model 1515HPLC), an auto-sampler (Model 717),
a UV detector (Model 2487), and a refractive index detector (Model
2410). The chromatograph was equipped with two 5 micrometer PLgel
MIXED-D columns (available from Varian Incorporated, Palo Alto,
Calif.). Samples of polymeric solutions were prepared by dissolving
polymer or dried polymer materials in tetrahydrofuran at a
concentration of 0.5 percent (weight/volume) and filtering through
a 0.2 micrometer polytetrafluoroethylene filter (available from VWR
International, West Chester, Pa.). The resulting samples were
injected into the GPC and eluted at a rate of 1 milliliter per
minute through the columns which were maintained at 35.degree. C.
The system was calibrated with polystyrene standards using a linear
least square fit analysis to establish a calibration curve. The
weight average molecular weight (Mw) and the polydispersity index
(weight average molecular weight divided by number average
molecular weight) were calculated for each sample against the
standard calibration curve.
Glass Transition Temperature (Tg)
[0261] Fox Glass Transition Temperature (Tg) is a calculated value
using the Fox equation. The calculation is based on the weighted
average of the individual homopolymer glass transition values. For
a copolymer prepared from n different monomers, the inverse of the
Tg of the copolymer is equal to the summation of the weight
fraction of each component divided by the Tg of that particular
component. That is, for a copolymer prepared from n components,
1/Tg of the copolymer is equal to (weight fraction of component
one/Tg of component one)+(weight fraction of component two/Tg of
component two)+(weight fraction of component 3/Tg of component 3)+
. . . +(weight fraction of component n/Tg of component n).
General Preparation of Cushion Layer 1 (C1)
[0262] Cushion Layer 1 was prepared by adding 95 parts by weight
(pbw) 2EHA, 5 pbw AA, 2 pbw of a 10 wt-% solution of VAZO 67 in
ethyl acetate, 0.8 pbw of a 10 wt-% solution of TDDM in ethyl
acetate, and 100 pbw ethyl acetate to a glass bottle. The solution
was purged with nitrogen for four minutes before securely sealing
the bottle, placing it in a rotating water bath at 60.degree. C.
for 24 hours, then allowing it to cool to ambient temperature to
obtain an adhesive polymer solution having a solids content of
approximately 50 wt-%. The resulting adhesive polymer solution was
used to evaluate the polymer for its molecular weight and glass
transition temperature as described in the test methods. The
monomer composition, molecular weight, and glass transition
temperature (Tg) are shown in Table 1.
Cushion Layers 2-4 (C2-C4)
[0263] Cushion Layers 2, 3, and 4 were prepared in a manner similar
to that described above for preparing Cushion Layer 1. The solvent
system for C3 was a mixture of ethyl acetate and heptane. The
solvent system for C4 was a mixture of heptane and acetone. The
resulting adhesive polymer solutions were used to evaluate the
polymers for their molecular weights and glass transition
temperatures as described in the test methods. The monomer
compositions, molecular weights, and glass transition temperatures
(Tg) are shown in Table 1.
Preparation of Shell Layer 1 (S1)
[0264] Shell Layer 1 was prepared by adding 50 parts by weight
(pbw) 2EHA, 45 pbw IBOA, 5 pbw AA, 2 pbw of a 10 wt-% solution of
VAZO 67 in ethyl acetate, 0.8 pbw of a 10 wt-% solution of TDDM in
ethyl acetate, and 100 pbw ethyl acetate to a glass bottle. The
solution was purged with nitrogen for four minutes before securely
sealing the bottle, placing it in a rotating water bath at
60.degree. C. for 24 hours, then allowing it to cool to ambient
temperature to obtain an adhesive polymer solution having a solids
content of approximately 50 wt-%. The resulting adhesive polymer
solution was used to evaluate the polymer to determine the
molecular weight and glass transition temperature as described in
the test methods. The monomer composition, molecular weight, and
glass transition temperature (Tg) are shown in Table 1.
Preparation of Shell Layers 2-6 (S2-S6)
[0265] Shell Layer 2 was prepared in a manner similar to that
described above for preparing Shell Layer 1. Shell Layers 3-6 were
prepared in a manner similar to that described above for preparing
Shell Layer 1 with the following modifications. VAZO 52 (0.1 pbw
dry weight) was used in place of VAZO 67, and IOTG (0.03 pbw dry
weight) was used in place of TDDM. The resulting adhesive polymer
solutions were used to evaluate the polymers for their molecular
weights and glass transition temperatures as described in the test
methods. The monomer compositions, molecular weights, and glass
transition temperatures (Tg) are shown in Table 1.
Coating Methods
Method 1: Cushion Layer/Shell Layer Coatings
[0266] The adhesive polymer solutions for C1 and C2, prepared as
described above, were coated onto the treated side of PPET film
using a knife coating station having a gap setting of 0.008 inch
(203 micrometers) greater than the film thickness. The coated PPET
film samples were dried at 70.degree. C. for at least 20 minutes to
provide an estimated dried coating thickness of approximately 0.002
inch (51 micrometers).
[0267] The adhesive polymer solutions for S1 and S2, prepared as
described above, diluted to 10 wt-% solids using a solvent mixture
of ethyl acetate and 1-methoxy-2-propanol to provide a final
solvent ratio of ethyl acetate:1-methoxy-2-propanol/75:25 (w:w),
then coated onto the release treated side a release liner film
using a #10 Mayer rod. The coated release film samples were dried
at 70.degree. C. for at least 20 minutes to achieve a dried coating
thickness of approximately 1.25+/-0.25 micrometers as determined by
microscopy using an optical interferometer.
[0268] After drying, the coated PPET films and release films were
laminated together by hand at 24.degree. C. using a rubber roller
such that the cushion and shell layers contacted each other. The
resulting constructions were crosslinked by electron beam (ebeam)
(Model CB-300 ELECTROCURTAIN, from Energy Sciences, Incorporated,
Wilmington, Mass.) using various beam current settings and an
accelerating voltage of 220 kiloVolts. Samples were conveyed
through the ebeam unit using a polyester carrier at a speed of 25.9
feet/minute (9 meters/minute) and irradiated from the release liner
side, to provide the doses shown in Table 2. Samples of cushion
layers alone between PPET and release liner films were also
irradiated to provide comparative examples. The resulting tape
constructions were evaluated for peel adhesion strength as
described in the test methods. The results are shown in Tables
2-4.
Method 2: Cushion Layer/Shell Layer Coatings
[0269] The adhesive polymer solution for C3, prepared as described
above, was coated onto the treated side of PPET film using a knife
coating station having a gap setting of 0.014 inch (356
micrometers) greater than the film thickness. The adhesive polymer
solution for C4, prepared as described above, was coated onto the
treated side of PPET film using a knife coating station having a
gap setting of 0.007 inch (178 micrometers) greater than the film
thickness. The films were coated and dried at 20 feet/minute (6.1
meters/minute) by passing them through three heating zones. Zone 1:
having temperature of 120.degree. F. (49.degree. C.) and a length
of 9 feet (2.7 meters); Zone 2: having temperature of 140.degree.
F. (60.degree. C.) and a length of 9 feet (2.7 meters); and Zone 3:
having temperature of 210.degree. F. (99.degree. C.) and a length
of 18 feet (5.4 meters). The average measured coating weight after
drying was 45.6 grams/square meter, which corresponded to a coating
thickness of approximately 0.0019 inch (48 micrometers) for both
cushion layers.
[0270] The adhesive polymer solutions for S3-S6, prepared as
described above, were used to prepare multilayer coated film
constructions as follows. A shell layer adhesive polymer solution
was diluted to 20 wt-% solids with ethyl acetate. An example was
also run at 15 wt-% solids. The resulting solution was delivered to
a 4-inch (10.2-centimeters) wide slot die coater, by means of a
syringe pump at a flow rate of between 1.8 to 9.2
milliliters/minute, and thereby delivered through a 0.005-inch
(127-micrometers) slot gap onto the surface of a dried cushion
layer 3 or cushion layer 4 coated film to provide a smooth,
continuous coating. The shell layer/cushion layer coated film was
dried by passing it through two, five-foot long, in-line drying
zones, both set at 88.degree. C., at a rate of 5 feet/minute. The
resulting constructions were crosslinked by electron beam (ebeam)
as described in "Method 1: Cushion Layer/Shell Layer Coatings."
Samples of cushion layers between PPET and release liner films were
also irradiated to provide comparative examples. The resulting tape
constructions were evaluated for peel adhesion strength, and in
some cases rolling ball tack, as described in the test methods. In
addition, the thicknesses of S3 and S4 were measured as described
in the test method "Shell Layer Thickness." The thicknesses of S5
and S6 were assumed to be similar since the same coating process
was used as for S3 and S4. The results are shown in Tables 2-5.
Compositions
TABLE-US-00003 [0271] TABLE 1 Cushion (C) and Shell (S) Layer
Compositions Molecular Glass Weight Transition IOA 2EHA IBOA AA ACM
NNDMA (Mw) Polydispersity Temperature Layer parts by weight (pbw)
(kg/mol) Index (.degree. C.) Cl -- 95 -- 5 -- -- NT NT -45 C2 -- 95
-- -- 2.5 2.5 NT NT -45 C3 96 -- -- -- 4 -- 1450 16.2 -50 C4 94 --
-- 6 -- -- 527 10.7 -49 S1 -- 50 45 5 -- -- 408 10.7 5 S2 -- 50 45
2.5 2.5 454 10.0 5 S3 -- 55 40 5 -- -- 469 6.74 -2 S4 -- 45 50 5 --
-- 449 6.47 12 S5 -- 47 50 -- 3 -- NT NT 10 S6 -- 22 75 -- 3 -- NT
NT 50 NT: not tested
Results
TABLE-US-00004 [0272] TABLE 2 Peel Adhesion Strength-at 65.degree.
C. on Polypropylene Shell Peel Peel Peel Peel Shell Layer Adhesion
Adhesion Adhesion Adhesion Layer Coating Strength Strength Strength
Strength Coating Pump Shell Layer Ebeam (N/cm) (N/cm) (N/cm) (N/cm)
Cushion/ Solution Speed Thickness Dose at 8.47 at 0.847 at 0.0847
at 0.00847 Ex. Shell (% Solids) (cc/min) (micrometers) MRads mm/sec
mm/sec mm/sec mm/sec CE 1 C1/-- NA NA NA 5 3.41 0.72 0.11 0.04 CE 2
C2/-- NA NA NA 5 2.24 0.34 0.08 0.04 CE 3 C3/-- NA NA NA 7 2.76
0.93 0.47 0.42 CE 4 C4/ -- NA NA NA 10 3.48 1.45 0.34 0.16 1 C1/S1
10 NA 1.2 5 4.04 2.18 0.88 0.41 2 C1/S2 10 NA 1.2 5 6.22 3.36 0.52
0.13 3 C2/S1 10 NA 1.2 5 4.98 2.89 0.70 0.11 4 C2/S2 10 NA 1.2 5
4.30 2.86 1.17 0.67 5 C3/S3 15 1.8 NT 7 5.08 4.00 1.94 0.38 6 C3/S3
20 2.3 4.9 7 5.07 3.92 2.97 1.17 7 C3/S3 20 9.2 11.2 7 2.76 3.87
3.54 1.76 8 C3/S4 20 2.3 4.1 7 2.45 3.52 2.48 1.49 9 C4/S5 20 2.3
ca. 4.5 10 5.39 3.12 1.51 0.20 10 C4/S6 20 2.3 ca. 4.5 10 2.46 3.03
2.88 1.16 CE: Comparative Example; NA: not applicable; NT: not
tested Ebeam Doses reported in Table 2 apply to the same C/S
combinations in Tables 3-5
TABLE-US-00005 TABLE 3 Peel Adhesion Strength-at 24.degree. C. on
Stainless Steel Shell Peel Peel Peel Peel Shell Layer Adhesion
Adhesion Adhesion Adhesion Layer Coating Strength Strength Strength
Strength Coating Pump Shell Layer (N/cm) (N/cm) (N/cm) (N/cm)
Cushion/ Solution Speed Thickness at 8.47 at 0.847 at 0.0847 at
0.00847 Ex. Shell (% Solids) (cc/min) (micrometers) mm/sec mm/sec
mm/sec mm/sec CE 5 C1/-- NA NA NA 8.56 4.81 2.40 1.01 CE 6 C2/-- NA
NA NA 7.03 3.47 1.25 0.51 CE 7 C3/-- NA NA NA 7.77 4.13 1.86 0.79
CE 8 C4/-- NA NA NA 10.72 6.24 3.48 1.57 11 C1/S1 10 NA 1.2 13.76
8.54 5.25 2.02 12 C1/S2 10 NA 1.2 9.11 5.77 3.33* 1.59 13 C2/S1 10
NA 1.2 14.13 8.60 4.76 2.23 14 C2/S2 10 NA 1.2 12.13 7.60 5.20 2.44
15 C3/S3 15 1.8 NT 10.18 8.88 7.22 4.95 16 C3/S3 20 2.3 4.9 10.29
8.67 7.57 5.40 17 C3/S3 20 9.2 11.2 10.42 9.26 7.56 5.34 18 C3/S4
20 2.3 4.1 10.23 9.10 7.67 5.27 19 C4/S5 20 2.3 ca. 4.5 12.08 8.15
6.21 4.26 20 C4/S6 20 2.3 ca. 4.5 12.09 9.27 6.08 4.22 CE:
Comparative Example; NA: not applicable; NT: not tested *For some
constructions, the peel adhesion strength was less than expected
due to the coating method used to join the cushion and shell
layers. For instance, Example 12 at 0.0847 mm/sec did not exhibit
twice the peel adhesion strength of Comparative Example 5. This is
believed to be due to the use of Coating Method 1 (dry lamination
process) which, in some cases, may not provide sufficient
interlayer adhesion between cushion and shell layers.
TABLE-US-00006 TABLE 4 Peel Adhesion Strength-at 65.degree. C. on
Stainless Steel Shell Peel Peel Peel Peel Shell Layer Adhesion
Adhesion Adhesion Adhesion Layer Coating Shell Strength Strength
Strength Strength Coating Pump Layer (N/cm) (N/cm) (N/cm) (N/cm)
Cushion/ Solution Speed Thickness at 8.47 at 0.847 at 0.0847 at
0.00847 Ex. Shell (% Solids) (cc/min) (micrometers) mm/sec mm/sec
mm/sec mm/sec CE 9 C1/-- NA NA NA 7.14 3.76 1.98 1.08 CE 10 C2/--
NA NA NA 3.77 2.04 1.04 0.54 CE 11 C3/-- NA NA NA 3.92 2.07 1.14
0.67 21 C1/S1 10 NA 1.2 6.81 3.20 1.34* 0.67 22 C1/S2 10 NA 1.2
6.80 3.22 0.65* 0.18 23 C2/S1 10 NA 1.2 6.24 3.36 0.63* 0.13 24
C2/S2 10 NA 1.2 5.39 2.69 1.23* 0.69 25 C3/S3 15 1.8 NT 7.11 4.28
2.33 0.68 26 C3/S3 20 2.3 4.9 8.00 5.26 4.03 1.69 27 C3/S3 20 9.2
11.2 7.36 5.91 3.59 2.15 28 C3/S4 20 2.3 4.1 8.10 5.75 4.18 1.88
CE: Comparative Example; NA: not applicable; NT: not tested *For
some constructions, the peel adhesion strength was less than
expected due to the coating method used to join the cushion and
shell layers. For instance, Examples 21-24 at 0.0847 mm/sec did not
exhibit twice the peel adhesion strength of Comparative Examples 9
and 10. This is believed to be due to the use of Coating Method 1
(dry lamination process) which, in some cases, may not provide
sufficient interlayer adhesion between cushion and shell
layers.
TABLE-US-00007 TABLE 5 Tack - Rolling Ball Distance Shell Shell
Layer Layer Coating Coating Pump Shell Layer Rolling Ball Cushion/
Solution Speed Thickness Distance Ex. Shell (% Solids) (cc/min)
(micrometers) (millimeters) CE 12 C3/-- NA NA NA 94 CE 13 C4/-- NA
NA NA 205 29 C3/S3 20 2.3 4.9 499 30 C3/S3 20 9.2 11.2 >1000 31
C3/S3 15 1.8 NT 436 32 C3/S4 20 2.3 4.1 834 CE: Comparative
Example; NA: not applicable; NT: not tested
[0273] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. To the
extent that there is any conflict or discrepancy between this
specification as written and the disclosure in any document that is
incorporated by reference herein, this specification as written
will control. Various modifications and alterations to this
disclosure will become apparent to those skilled in the art without
departing from the scope and spirit of this disclosure. It should
be understood that this disclosure is not intended to be unduly
limited by the illustrative embodiments and examples set forth
herein and that such examples and embodiments are presented by way
of example only with the scope of the disclosure intended to be
limited only by the claims set forth herein as follows.
* * * * *